Skip to main content
Download PDF

MRI findings for the pretreatment diagnosis of small Meckel’s cave tumors: comparison of meningiomas and schwannomas

BMC Medical Imaging volume 25, Article number: 57 (2025) Cite this article

Abstract

Background

Both meningiomas and schwannomas are the most common Meckel's cave (MC) tumors in terms of distinct imaging features. When they are small, they may present with similar imaging characteristics that make their diagnosis difficult. The aim of this study was to diagnose small meningiomas and schwannomas of the MC on the basis of their clinical and MRI findings.

Methods

The clinical data of 33 patients who were diagnosed with small MC tumors (SMCTs) (17 schwannomas, 16 meningiomas) between August 2002 and August 2023 were retrospectively evaluated. SMCTs were defined as MC tumors that were less than 3 cm in size. We analyzed their clinical and MRI findings, including demographic features, lesion morphologies and changes in adjacent structures.

Results

The rate of subtotal resection of meningiomas less than 3 cm in size was significantly lower than that of schwannomas less than 3 cm in size (43.8% vs. 100%, p = 0.032). The MRI features of meningiomas and schwannomas were as follows: 1) a prominent dura tail sign (8/16 [50%] vs. 0/17 [0%], p < 0.001); 2) few cystic components (0/16 [0%] vs. 9/17 [52.94%], p < 0.001); 3) lower minimum ADC (ADCmin) values (820.575 ± 302.545 [86.1–1144.4] vs. 1372.424 ± 561.337 [355.7–2616.6], p < 0.001); and 4) minimal ipsilateral masticatory muscle atrophy (-6.71% ± 22.43% [-85.71% ~ 13.79%] vs. 11.24% ± 11.98% [-14% ~ 38%], p < 0.001). Very small MC tumors (VSMCTs) were ≤ 2 cm in size, and the subgroup analysis of very small meningiomas and schwannomas revealed no differences in terms of ipsilateral masticatory muscle atrophy (p = 0.078), prominence of the dural tail (p = 0.236), or the presence of cystic components (p = 0. 364). However, the ADCmin values were significantly lower for very small meningiomas than for very small schwannomas (p = 0.009).

Conclusion

MRI features such as a prominent dural tail appearance, the presence of fewer cystic components, and less masticatory muscle atrophy may aid in differentiating meningiomas from schwannomas less than 3 cm in size. The ADC and DWI parameters provided additional critical insights, particularly for VSMCTs, thus facilitating preoperative diagnoses.

Peer Review reports

Background

Meckel's cave (MC) is a cisternal space situated at the base of the skull and houses the trigeminal nerve. Both meningiomas and schwannomas are tumors that most commonly develop in this space [1]. The pretreatment diagnosis of both tumors is not difficult if they are large and present with characteristic clinical and imaging features [2, 3]. Meningiomas usually appear as well-circumscribed and dura-based masses. They tend to have a characteristic dural tail appearance, which is characterized by the presence of enhancing tissue extending along the dura mater, appearing as a tail. Schwannomas usually present as well-circumscribed, enhancing masses. In some cases, schwannomas may contain cystic components or areas of necrosis.

The primary treatment for meningiomas and schwannomas of MC is surgical resection [4, 5]. To reduce the risk of clinical deficits, neurosurgeons aim to remove the tumor while preserving the integrity of the trigeminal nerve. In some cases where surgical resection is high risk or not possible, stereotactic radiosurgery, such as Gamma Knife or CyberKnife, can be performed to treat the tumors. However, the outcome of MC tumors varies greatly. Meningiomas have a 5-year recurrence rate of 13.1% [6], which is higher than that of schwannomas (7.4%) [7]. The higher rate of meningioma recurrence is due to difficulties associated with the total resection of the entire dural origin and hyperostotic bone [8]. The pretreatment diagnosis of both tumors is important for planning the most appropriate therapeutic approach and for predicting patient outcomes. Although some advanced imaging techniques (such as DWI or MR perfusion) are beneficial for distinguishing these tumors, the imaging features of these two tumors may be similar when they are small [9,10,11]. The presence of susceptibility artifacts could limit the clear visualization of these small tumors on images of the skull base. The aim of this retrospective study was to determine the pretreatment diagnosis of SMCTs, particularly small meningiomas and small schwannomas, on the basis of their MRI features to facilitate timely treatment planning and to improve outcomes.

Methods

Patients

Between August 2002 and August 2023, 55 patients were pathologically diagnosed with schwannomas in MC and 59 patients were pathologically diagnosed with meningiomas in MC at our institute (Fig. 1). We excluded patients with tumors larger than 3 cm and incomplete MR data and patients with significant susceptibility artifacts on the images of the skull base. A total of 33 patients with SMCTs, including 17 schwannomas and 16 meningiomas, were included in this study (Fig. 1). We reviewed the patients’ demographic data, surgical results, and outcomes (Supplementary Table 1 and Supplementary Table 2).

Fig. 1
figure 1

Patient flow diagram. We included 33 cases of small Meckel’s tumor in our study, including 16 meningiomas and 17 schwannomas. We excluded patients with significant susceptibility artifacts that could interfere with the accurate application and interpretation of DWI/ADC imaging parameters

Full size image

MRI

Conventional MR scans of the brain were performed using a 1.5 T clinical MR scanner (Siemens Medical Solutions; GE Medical Systems; or Philips Medical Systems). The protocol included axial T1/T2-weighted imaging; axial, sagittal and coronal contrast-enhanced fat-suppressed T1WI; diffusion-weighted imaging (DWI); and apparent diffusion coefficient (ADC) mapping.

We comprehensively analyzed the features of the tumors including the presence or absence of the dural tail sign [12, 13], presence or absence of the dumbbell shape [9, 10, 14], presence or absence of cystic components [15], and signal intensity within the solid components on axial T1-weighted imaging (T1WI), axial T2-weighted imaging (T2WI), and contrast-enhanced axial T1-weighted imaging [3]. A cystic component was defined as a well-demarcated, fluid-like area within the tumor, characterized by high T2-weighted signal intensity similar to cerebrospinal fluid, absence of restricted diffusion, and lack of enhancement after contrast administration. To determine the absolute minimum ADC values (referred to as the ADCmin), we used manually placed regions of interest (ROIs) with sizes ranging from 10 to 50 square millimeters [16]. This process was facilitated by the use of the hospital's picture archiving and communication system (PACS) workstations. We strategically positioned the tumor ROIs in areas with the lowest signals within the solid tumor components while ensuring that areas with necrosis, peritumoral edema, calcification, and hemorrhage were avoided [16]. Three distinct ROIs were situated on different sections and subsequently averaged. To account for variations in signal settings among different MRI scanners, we included an additional region of interest (ROI) that was placed in the corresponding region of the normal-appearing contralateral white matter on the medial side of the temporal lobe. The ADC ratio was the ratio between the solid tumor and the contralateral white matter [16,17,18]. Similarly, we determined DWI ratios (using a b value of 1000 s/mm2) by positioning the tumor ROIs in areas with the highest signals.

Differentiating small brain tumors is sometimes difficult when there are no characteristic imaging features. Therefore, we searched for secondary features, such as masticatory muscle atrophy, to ensure an accurate diagnosis. As the SMCT may involve or compress the trigeminal nerve, we suggest that subsequent denervation changes in the motor division of the trigeminal nerve may cause ipsilateral masticator muscle atrophy [19, 20]. Notably, the temporalis muscle is the most dominant masticatory muscle and is easily recognized on MR images of the brain. We determined the presence or absence of masticatory muscle atrophy by determining whether there was a decrease in muscle thickness [21]. Temporalis muscle thickness was measured at the level of the anterior limit of the septum pellucidum on axial T1-weighted images [22] (Fig. 2 and Fig. 3). We then calculated the percentage of atrophy as follows: [(normal muscle thickness—tumor side muscle thickness)/normal muscle thickness] × 100% [22]; positive values indicate a decrease in thickness (atrophy), whereas negative values indicate an increase in thickness.

Fig. 2
figure 2

Evaluation of schwannomas. A-I A female between the ages of 50 and 60 diagnosed with a trigeminal schwannoma on the left side of the MC and cerebellopontine cistern. A Postcontrast T1WI image showing a 2.9 cm heterogeneously enhancing tumor in the left MC and cerebellopontine cistern. B T2WI image showing high signals with cystic changes in the tumor. C, D No restricted diffusion in the DWI/ADC sequence. E, F The first tumor ROI, denoted as T, was meticulously placed over the corresponding region exhibiting the most intense signal within the solid components observed on DWI (E) and over the region displaying the least signal for ADC calculation (F). Subsequent tumor ROIs, labeled second and third, were established on distinct image sections (details not displayed). Supplementary ROIs were meticulously positioned over analogous regions of normal-appearing contralateral white matter situated in the medial aspect of the temporal lobe, denoted as WM, on DWI (b = 1000 s/mm2). The patient had a DWI ratio of 0.99, an apparent diffusion coefficient (ADCmin) of 1215 × 10−6 mm2/s, and an apparent diffusion coefficient (ADC) ratio of 1.61. G To measure temporalis muscle thickness, first, we used sagittal images to locate the level of the anterior limit of the septum pellucidum, at which point we applied axial T1WI and axial T2WI images for temporalis muscle evaluation. H In the axial T1WI image, we measured the thickest part of the bilateral temporalis muscles. The temporalis muscle was 4.8 mm on the tumor side and 6.8 cm on the contralateral side, suggesting masticatory muscle atrophy. I In the axial T2WI image, we evaluated fatty acid changes in the temporalis muscle. There was no increased signal in the temporalis muscle on the tumor side, implying that there was no significant fatty infiltration.

Full size image
Fig. 3
figure 3

Evaluation of meningioma. A-F A female between the ages of 50 and 60 diagnosed with meningioma on the right side of the MC and parasellar region. A Postcontrast T1WI image showing a 2.7 cm enhancing tumor with a dura tail appearance at the right MC. B, C Restricted diffusion in the DWI/ADC sequence. D, E The patient had a DWI ratio of 1.82, an ADCmin of 1042 × 10−6 mm2/s, and an ADC ratio of 1. F In the axial T1WI image, we measured the thickest part of the bilateral temporalis muscles. In this case, there was no masticatory muscle atrophy at the tumor side

Full size image

Surgical treatment and follow-up

Total or subtotal removal of the tumor is defined as the removal of more than 90% of the tumor, and partial removal or biopsy is defined as the removal of less than 90% of the tumor [23, 24]. The patients’ clinical records and 1-month postoperative MRI were reviewed to ascertain the surgical outcomes. All patients underwent regular follow-up in the OPD every 3 months during the first 2 years and then every 6 to 12 months thereafter. MRI of the brain was regularly performed during the postsurgical follow-up. Any signs of tumor recurrence or neurological complications were recorded. Tumor recurrence was defined as the presence of a residual, enhancing, or solid tumor with a volume increase of more than 20% compared with the first postoperative MRI [23].

Statistical assessment

All the statistical analyses were conducted using IBM® SPSS® software. Continuous variables are presented as means with standard deviations, and P values were calculated using the Mann–Whitney U test. Categorical variables are presented as counts and percentages, and P values were calculated using Fisher's exact test. Patients with missing values for any variable were excluded from the analysis of that specific variable. All reported P values were two-sided. P values less than 0.05 indicated statistical significance.

Results

Demographic features and clinical outcomes

The demographic characteristics and clinical outcomes of the 33 patients with SMCTs, including 16 with meningiomas and 17 with schwannomas, are shown in Table 1. There was no significant difference in symptoms such as blurred vision, facial numbness, or pain between the patients with meningiomas and the patients with schwannomas. The rate of total or subtotal resection of schwannomas was significantly higher than that of meningiomas (100% vs. 43.8%, p = 0.032). However, there was no significant difference in tumor recurrence rate or the survival rate between the patients with meningiomas and those with schwannomas.

Table 1 Demographics and MRI of 16 meningioma and 17 schwannoma patients under 3 cm
Full size table

MR findings

The MR features of the 33 SMCTs are shown in Table 1. The proportion of meningiomas with the dural tail sign was greater than that of schwannomas with the dural tail sign (50% vs. 0%, p < 0.001), and the proportion of schwannomas with cystic components was greater than that of meningiomas with cystic components (52.94% vs. 0%, p < 0.001). Compared with schwannomas, meningiomas also had significantly lower ADCmin values (820.575 ± 302.545 [86.1–1144.4] vs. 1372.424 ± 561.337 [355.7–2616.6], p < 0.001), lower ADC ratios (1.246 ± 0.234 [0.885–1.678] vs. 1.683 ± 0.576 [0.497–3.089], p < 0.001) and higher DWI ratios (1.392 ± 0.364 [0.891–2.360] vs. 0.829 ± 0.352 [0.299–1.801], p < 0.001). There was no significant difference between the number of meningiomas with a dumbbell shape and the number of schwannomas with a dumbbell shape (18.75% vs. 29.41%, p = 0.688) (Fig. 4). Compared with meningiomas, schwannomas were associated with masticatory muscle atrophy, as indicated by significant decreases in muscle thickness (11.24% ± 11.98% [−14% ~ 38%] vs. −6.71% ± 22.43% [−85.71% ~ 13.79%], p < 0.001).

Fig. 4
figure 4

Dumbbell shape of the SMCT image (A, B) Postcontrast T1WI image in two different patients. A A female between the ages of 50 and 60 diagnosed with a trigeminal schwannoma on the left side of the MC and cerebellopontine cistern. B A 41-year-old female diagnosed with meningioma on the right side of the MC and cerebellopontine cistern. Dumbbell-shaped tumors can be noted in both schwannomas and meningiomas

Full size image

The subgroup analysis of SMCTs less than 2.5 cm revealed similar results to that of SMCTs less than 3 cm (Table 2). The significant differences in the MR features between meningiomas and schwannomas were as follows: 1) a more prominent dura tail sign (4/9 [44.44%] vs. 0/13 [0%], p = 0.017); 2) few cystic components (0/9 [0%] vs. 5/13 [38.46%], p = 0.054); 3) lower minimum ADC (ADCmin) values (750.022 ± 381.242 [86.1–1144.4] vs. 1365.992 ± 623.02 [355.7–2616.6], p = 0.002); and 4) minimal masticatory muscle atrophy (−13.0 ± 26.0 [−86.0 ~ 3.0] vs. 11.24% ± 11.0 ± 12.0 (−14.0 ~ 38.0), p < 0.001).

Table 2 MRI features of 9 meningiomas and 13 schwannomas less than 2.5 cm in size
Full size table

We further analyzed the subgroup of very small Meckel’s cave tumors less than 2 cm (VSMCTs). There was no difference between meningiomas and schwannomas in terms of the presence or absence of masticatory muscle atrophy (−15% ± 29% [−86% ~ 3%] vs. 11% ± 18% [−14% ~ 38%], p = 0.078), the dural tail (3/7 [42.86%] vs. 0/4 [0%], p = 0.236) or the cystic component (0/7 [0%] vs. 1/4 [25%], p = 0. 364). However, compared with schwannomas, meningiomas had significantly lower ADCmin values (703.0 ± 424.558 [86.1–1144.4] vs. 1915.625 ± 771.0 [1118.8–2616.6], p = 0.009), lower ADC ratios (1.253 ± 0.243 [0.96–1.62] vs. 2.02 ± 0.713 [1.63–3.09], p = 0.005) and higher DWI ratios (1.353 ± 0.262 [0.99–1.84] vs. 0.737 ± 0.26 [0.35–0.93], p = 0.005) (Table 3 and Fig. 5).

Table 3 MRI features of 7 meningiomas and 4 schwannomas less than 2 cm in size
Full size table
Fig. 5
figure 5

Evaluation of a small tumor (< 2 cm) (A-D) A female between the ages of 50 and 60 diagnosed with meningioma on the right side of the MC and parasellar region. A Postcontrast T1WI image showing a 1.2 cm enhancing tumor at the right MC. For the present small tumor, the appearance of the dura tail was not clearly identified. B, C Restricted diffusion in the DWI/ADC sequence in small tumors (in the parasellar region). D In the axial T1WI image, no significant masticatory muscular atrophy was identified. E-I A female between the ages of 50 and 60 diagnosed with a schwannoma on the right side of the MC. E In the postcontrast T1WI image, a 1.4 cm enhancing tumor at the right MC. F On T2W images, cystic changes were not clearly identified in such small schwannomas. G, H No restricted diffusion in the DWI/ADC sequence. I In the axial T1WI image, no significant masticatory muscular atrophy was identified

Full size image

Discussion

This study extensively investigated the diagnostic markers for the most common SMCTs, meningiomas and schwannomas. Our study revealed the significance of the dura tail sign, presence or absence of cystic components, presence or absence of ipsilateral masticatory muscle atrophy and DWI/ADC parameters are important imaging features that may aid in differentiating tumors smaller than 3 cm. Notably, the presence of ipsilateral masticatory muscle atrophy was strongly associated with schwannomas, providing a crucial clinical indicator for differential diagnoses alongside traditional imaging diagnoses on the basis of features such as the dural tail sign in meningiomas and the presence of cystic components in schwannomas. The ADC and DWI parameters offered critical insights. Compared with schwannomas, meningiomas presented significantly lower ADCmin values, indicating more restricted diffusion. This DWI/ADC parameter is particularly valuable in the diagnosis of very small meningiomas and schwannomas (< 2 cm in size), whereas the presence of the dural tail sign in meningiomas and cystic components, as well as masticatory muscle atrophy in schwannomas, is not readily discernible in VSMCTs. Our findings are summarized in Supplementary Table 3.

The present study revealed that the rate of total or subtotal resection of meningiomas was significantly lower than that of schwannomas. This aligns with earlier research, highlighting that meningiomas often have more complex attachments to the dura and surrounding bony structures, making complete resection more difficult [8]. Meningiomas originate from arachnoid cap cells and frequently invade adjacent dura and bone, requiring meticulous surgery to achieve clear margins without causing excessive damage to critical structures. In contrast, schwannomas, arising from Schwann cells of the trigeminal nerve, are typically well circumscribed and more easily separated from surrounding tissues, leading to higher rates of complete resection. Although the recurrence rates between these tumors did not show a significant difference in out study, possibly due to the relatively small sample size, the higher rate of meningioma recurrence noted in previous studies is also attributable to the difficulty of complete resection [6, 7].

The MC, a crucial cisternal space at the skull base, harbors the trigeminal nerve, which is essential for facial sensation and mastication. The trigeminal ganglion within the MC and the adjacent cavernous sinus, which contains several cranial nerves, including motor and sensory fibers of the trigeminal nerve and the internal carotid artery, are areas of interest when evaluating tumors in this location1. Both meningiomas and schwannomas are the most common MC tumors. Typical MR features, such as the dural tail sign in meningiomas and the presence of cystic components in schwannomas, are important for the diagnosis of both tumors. The presence of the dural tail sign in meningiomas is due to its attachment to the dura mater. The tumor often involves the dural blood supply, leading to enhancement of the dural attachment in post-contrast T1-weighted images [25]. The dural tail sign is usually absent in schwannomas, as they arise from Schwann cells within peripheral nerve sheaths, not from the dura mater [12]. Schwannomas are more prone to developing cystic components, which appear as well-defined, low-signal intensity areas on T1-weighted images and high-signal intensity areas on T2-weighted images. The reasons for the higher prevalence of cysts in schwannomas are not fully understood. The possible mechanisms of these cystic changes include intratumoral bleeding, degenerative changes, and central ischemic necrosis [15, 26].

In our investigation, the presence of the dural tail sign in meningiomas and cystic changes, as well as masticatory muscle atrophy in schwannomas, was not readily discernible in VSMCTs. However, the detection of restricted diffusion in meningiomas remains valuable under such circumstances. Meningiomas typically originate from arachnoid cap cells and adhere to the dura mater, resulting in the characteristic dural tail sign that is evident in imaging studies [25]. However, in smaller tumors, the extent of dural attachment may be limited, leading to an insufficient mass or surface area to generate a noticeable dural tail. In our study, tumors measuring 3 cm and 2.5 cm were sufficiently large to show the dural tail sign, while tumors smaller than 2 cm were too small to display this feature. Cystic changes within tumors, such as those observed in schwannomas, often arise from degenerative processes, including hemorrhage, necrosis, or cystic degeneration within the tumor tissue [15]. Nevertheless, these changes may need time to manifest on imaging studies and thus are more frequently observed in larger tumors. In smaller tumors, there might be inadequate time for significant cystic changes to develop, particularly if the tumor grows slowly, hence making cystic components less conspicuous or absent in VSMCTs. In our study, tumors measuring 3 cm and 2.5 cm were large enough to show cystic changes in schwannomas, whereas tumors smaller than 2 cm were too small to exhibit them.

In MRI sequences, DWI measures the movement of water molecules within tissues, and the ADC quantifies the degree of water diffusion, reflecting the cellular density and tissue architecture. Even in small tumors, microstructural alterations exist within the tissue, leading to changes in water diffusion patterns that can be captured by DWI. The study revealed significant differences in the DWI/ADC values between meningiomas and schwannomas, with meningiomas showing more restricted diffusion, which is also useful for VSMCTs. Schwannomas typically appear hyperintense on DWI and have high ADC values because of the presence of loose, myxoid matrix and cystic components that allow easier water diffusion [27]. Meningiomas usually appear hyperintense on DWI and have lower ADC values because of their cellularity and compact structure, hindering water movement [28]. In our study, all tumors, whether 3 cm, 2.5 cm, or smaller than 2 cm, displayed restricted diffusion in meningiomas.

There are no characteristic MRI features of VSMCTs. First, typical imaging characteristics, such as the dural tail sign in meningiomas or cystic components in schwannomas, require sufficient time to develop, but small lesions might not have had adequate time to mature and grow to display these features prominently [29]. Second, the presence of significant susceptibility artifacts at the skull base can limit the clarity of the tissue on MR images of small tumors. Last, small lesions may be challenging to resolve owing to the limited spatial resolution of standard MRI.

To solve the above issues, techniques such as high-resolution MRI or parallel imaging techniques, such as compressed sensing or sensitivity encoding (SENSE), multishot, and turbo spin‒echo sequences, can significantly reduce these artifacts, enhancing the sensitivity and resolution of imaging [30]. In cases where small lesions are obscured by artifacts originating from the skull base in the axial DWI plane, employing the coronal DWI scanning orientation can markedly increase the sensitivity for detecting subtle abnormalities, refine the demarcation of tumor margins, and mitigate skull base artifacts. Consequently, this strategy enables a more precise evaluation of diminutive lesions such as brain stem stroke [31]. Nevertheless, there is a lack of research on small tumors at present, so further investigation is necessary. In addition, previous research has suggested that magnetic resonance perfusion (MRP) and magnetic resonance spectroscopy (MRS) are advanced MRI techniques that can provide valuable insights into the metabolic and hemodynamic attributes of brain tumors [32]. These advanced imaging modalities can significantly improve the detection and differentiation of small meningiomas and schwannomas, thus enhancing preoperative planning and outcomes.

To our knowledge, this is the first study in which masticator muscle atrophy was used to aid the diagnosis of MC tumors. Our findings suggest that it may provide additional diagnostic value in evaluating these tumors. Some cases of masticator muscle atrophy resulting from trigeminal nerve function impairment associated with schwannomas have been reported [33,34,35]. The trigeminal nerve, which is the largest among the cranial nerves, plays a crucial role in providing both sensory and motor innervation to the muscles involved in chewing. Within the MC, this nerve branches into the ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves. Notably, V3 is unique in that it encompasses both sensory and motor components, with its motor fibers specifically targeting the muscles responsible for mastication, namely, the medial pterygoid, lateral pterygoid, masseter, and temporalis muscles. The motor root of the trigeminal nerve travels inferiorly to the sensory root along the floor of the trigeminal cave [19, 20]. Schwannomas primarily arise from Schwann cells associated with the sensory root of the trigeminal nerve [36]. When these tumors affect the sensory fibers of the trigeminal nerve, they exert downward pressure on the motor fibers of V3 due to gravity, leading to partial motor function impairment and subsequent atrophy of the masticator muscles. Additionally, there have been rare instances of schwannomas involving the motor fibers of the trigeminal nerve directly [37], resulting in directly impaired motor function and consequent masticator muscle atrophy. In contrast, meningiomas originating in the MC stem from arachnoid cells of the arachnoid mater, which is positioned at the base of the skull within the MC, are less likely to involve or compress the motor fibers of the trigeminal nerve directly. Therefore, Schwannomas are more likely to cause evident masticatory muscle atrophy than meningiomas are (Fig. 6). This atrophy is caused by the tumor's impact on the nerve, inducing denervation and subsequent muscle wasting [21, 38]. However, in cases of smaller tumors, the extent of nerve involvement and resulting muscle atrophy may be less significant. This is especially true considering that smaller tumors may have a shorter duration of growth and activity in the MC, which might not accurately depict muscle changes on MRI. Therefore, masticatory muscle atrophy was not evident in the VSMCTs in our study. In our study, tumors measuring 3 cm and 2.5 cm were large enough to show masticatory muscle atrophy in schwannomas, whereas tumors smaller than 2 cm were too small to display this feature.

Fig. 6
figure 6

SMCT image and sensory and motor fibers of the trigeminal nerve. A Anatomy of the sensory and motor roots of the trigeminal nerve. The motor fibers of the trigeminal nerve travel beneath the sensory fibers. B Schwannomas arising from the sensory fibers of the trigeminal nerve exert downward pressure on the motor fibers of V3 due to gravity, leading to partial motor function impairment and subsequent atrophy of the masticator muscles. C Schwannomas arising from the motor fibers of the trigeminal nerve result in directly impaired motor function and consequent masticator muscle atrophy. D Meningiomas positioned at the base of the MC are less likely to compress the motor fibers of the trigeminal nerve

Full size image

Limitations

There are several limitations to our study. First, a relatively small number of patients were included. Future studies with larger cohorts are warranted to validate and extend our results. Second, the study focused on patients with pathologically confirmed schwannomas and meningiomas who underwent surgery, potentially leading to selection bias in the exclusion of those not indicated for surgery. Third, we excluded patients with significant susceptibility artifacts at the skull base. While this decision was made to ensure the integrity and reliability of DWI/ADC measurements for small tumors, it acknowledges the potential challenge that such artifacts pose in real-world clinical settings. These exclusion criteria might limit the generalizability of our findings to all patients with small tumors at the skull base, as artifacts can occasionally obscure tumor characteristics or mimic pathological findings.

Although previous literature has reported different outcomes for meningiomas and schwannomas, our study found no significant differences in recurrence rates or survival between these tumors. This could be attributed to the relatively small sample size and potential selection bias. Lastly, our study suggests an association between decreased masticatory muscle thickness and schwannomas. However, this finding does not necessarily indicate a direct causal relationship between schwannomas and masticatory muscle atrophy. We hypothesize that schwannomas may interact with the trigeminal nerve, potentially leading to muscle atrophy, but further studies are required to elucidate the exact mechanisms underlying this phenomenon.

Conclusions

In conclusion, our retrospective study emphasizes the importance of comprehensive clinical and MR evaluations in the diagnosis of SMCTs. This study highlights the importance of masticator muscular atrophy, in addition to traditional imaging features such as the dural tail sign and cystic components, in aiding the differentiation of small meningiomas and small schwannomas within the MC. ADC and DWI parameters also provide valuable insights for the radiological diagnosis of small lesions, especially VSMCTs.

Data availability

The data supporting the findings of this study were obtained from our institution and are not publicly available due to privacy and ethical restrictions.

Abbreviations

MC:

Meckel's cave

SMCTs:

Small Meckel's cave tumors

VSMCTs:

Very small MC tumors

DWI:

Diffusion-weighted imaging

ADC:

Apparent diffusion coefficient

ROI:

Region of interest

T1WI:

T1-weighted imaging

T2WI:

T2-weighted imaging

PACS:

Picture archiving and communication system

References

  1. Malhotra A, Tu L, Kalra VB, Wu X, Mian A, Mangla R, et al. Neuroimaging of Meckel’s cave in normal and disease conditions. Insights Imaging. 2018;9(4):499–510. https://doiorg.publicaciones.saludcastillayleon.es/10.1007/s13244-018-0604-7.

    Article  PubMed  PubMed Central  Google Scholar 

  2. Rigamonti D, Spetzler RF, Shetter A, Drayer BP. Magnetic resonance imaging and trigeminal schwannoma. Surg Neurol. 1987;28(1):67–70. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/0090-3019(87)90209-6.

    Article  CAS  PubMed  Google Scholar 

  3. Nguyen DH, TD Le, DM Nguyen, HK Nguyen, QD, Ngo DH. Duong, et al., Diagnostic performance of quantitative signal intensity measurements on magnetic resonance imaging for distinguishing cerebellopontine angle meningioma from acoustic schwannoma. Eur Rev Med Pharmacol Sci, 2022;26(19):7115–7124. https://doiorg.publicaciones.saludcastillayleon.es/10.26355/eurrev_202210_29897.

  4. Apra C, Peyre M, Kalamarides M. Current treatment options for meningioma. Expert Rev Neurother. 2018;18(3):241–9. https://doiorg.publicaciones.saludcastillayleon.es/10.1080/14737175.2018.1429920.

    Article  CAS  PubMed  Google Scholar 

  5. Li M, Wang X, Chen G, Liang J, Guo H, Song G, et al. Trigeminal schwannoma: a single-center experience with 43 cases and review of literature. Br J Neurosurg. 2021;35(1):49–56. https://doiorg.publicaciones.saludcastillayleon.es/10.1080/02688697.2020.1754334.

    Article  PubMed  Google Scholar 

  6. Qiao L, Yu C, Zhang H, Zhang M, Qu Y, Ren M, et al. Clinical outcomes and survival analysis for petroclival meningioma patients receiving surgical resection: an analysis of 176 cases. Cancer Manag Res. 2019;11:5949–59. https://doiorg.publicaciones.saludcastillayleon.es/10.2147/CMAR.S200932.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. Karras CL, Texakalidis P, Thirunavu VM, Nandoliya KR, Khazanchi R, Byrne K, et al. Outcomes following surgical resection of trigeminal schwannomas: a systematic review and meta-analysis. Neurosurg Rev. 2023;46(1):215. https://doiorg.publicaciones.saludcastillayleon.es/10.1007/s10143-023-02121-1.

    Article  PubMed  Google Scholar 

  8. Voss NF, FD Vrionis, CB, Heilman, JH Robertson, Meningiomas of the cerebellopontine angle. Surg Neurol, 2000. 53(5): 439–446; discussion 446-447. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/s0090-3019(00)00195-6.

  9. Hsiao CY, Chen LK, Tsai YF, Huang CW. Meningioma presenting as a skull base dumbbell shaped tumor. Journal of Radiological Science. 2016;41(4):135–7. https://doiorg.publicaciones.saludcastillayleon.es/10.6698/JRS.201612_4104.05.

    Article  Google Scholar 

  10. Chang CP, Chang CS, Yang MY, Shen CC. Dumbbell-shaped meningioma of Meckel’s cave mimicking trigeminal schwannoma: a case report. Int J Surg Case Rep. 2022;97:107369. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.ijscr.2022.107369.

    Article  PubMed  PubMed Central  Google Scholar 

  11. Salunke P, Pal BK, Vyas S, Radotra BD. Clear cell meningioma masquerading as trigeminal schwannoma. Surg Neurol Int. 2012;3:93. https://doiorg.publicaciones.saludcastillayleon.es/10.4103/2152-7806.99940.

    Article  PubMed  PubMed Central  Google Scholar 

  12. Lyndon D, Lansley JA, Evanson J, Krishnan AS. Dural masses: meningiomas and their mimics. Insights Imaging. 2019;10(1):11. https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13244-019-0697-7.

    Article  PubMed  PubMed Central  Google Scholar 

  13. Sotoudeh H, Yazdi HR. A review on dural tail sign. World J Radiol. 2010;2(5):188–92. https://doiorg.publicaciones.saludcastillayleon.es/10.4329/wjr.v2.i5.188.

    Article  PubMed  PubMed Central  Google Scholar 

  14. Al-Mefty O, Ayoubi S, Gaber E. Trigeminal schwannomas: removal of dumbbell-shaped tumors through the expanded Meckel cave and outcomes of cranial nerve function. J Neurosurg. 2002;96(3):453–63. https://doiorg.publicaciones.saludcastillayleon.es/10.3171/jns.2002.96.3.0453.

    Article  PubMed  Google Scholar 

  15. Ortega-Merchan MP, Reyes F, Mejia JA, Rivera DM, Galvis JC, Marquez JC. Cystic trigeminal schwannomas. Radiol Case Rep. 2019;14(12):1513–7. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.radcr.2019.09.031.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Wu HW, Wu CH, Lin SC, Wu CC, Chen HH, Chen YW, et al. MRI features of pediatric atypical teratoid rhabdoid tumors and medulloblastomas of the posterior fossa. Cancer Med. 2023;12(9):10449–61. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/cam4.5780.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  17. Ota Y, Liao E, Zhao R, Lobo R, Capizzano AA, Bapuraj JR, et al. Advanced MRI to differentiate schwannomas and metastases in the cerebellopontine angle/internal auditory canal. J Neuroimaging. 2022;32(6):1177–84. https://doiorg.publicaciones.saludcastillayleon.es/10.1111/jon.13028.

    Article  PubMed  PubMed Central  Google Scholar 

  18. Swaika S, A Gupta, S Agarwal, Apparent diffusion coefficient values and intra-tumoral susceptibility signals in meningiomas and schwannomas: useful tools for challenging cases. Int Clin Neurosci J, 2023;10:e4. https://doiorg.publicaciones.saludcastillayleon.es/10.34172/icnj.2023.04.

  19. Huff T, LJ Weisbrod, DT Daly. Neuroanatomy, Cranial Nerve 5 (Trigeminal). 2018, Treasure Island, FL: StatPearls Publishing.

  20. Kamel HA, Toland J. Trigeminal nerve anatomy: illustrated using examples of abnormalities. AJR Am J Roentgenol. 2001;176(1):247–51. https://doiorg.publicaciones.saludcastillayleon.es/10.2214/ajr.176.1.1760247.

    Article  CAS  PubMed  Google Scholar 

  21. Russo CP, Smoker WR, Weissman JL. MR appearance of trigeminal and hypoglossal motor denervation. AJNR Am J Neuroradiol. 1997;18(7):1375–83.

    CAS  PubMed  PubMed Central  Google Scholar 

  22. Zhang X, Wang C, Zheng D, Xiao H, Zhong Q. Magnetic resonance imaging evaluation of masticatory muscle changes in patients with primary trigeminal neuralgia before microvascular decompression. Medicine (Baltimore). 2022;101(41):e31010. https://doiorg.publicaciones.saludcastillayleon.es/10.1097/MD.0000000000031010.

    Article  PubMed  Google Scholar 

  23. Park HH, Park SH, Oh HC, Jung HH, Chang JH, Lee KS, et al. The behavior of residual tumors following incomplete surgical resection for vestibular schwannomas. Sci Rep. 2021;11(1):4665. https://doiorg.publicaciones.saludcastillayleon.es/10.1038/s41598-021-84319-1.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  24. Qin C, Wang J, Long W, Xiao K, Wu C, Yuan J, et al. Surgical management of tentorial notch meningioma guided by further classification: a consecutive study of 53 clinical cases. Front Oncol. 2020;10:609056. https://doiorg.publicaciones.saludcastillayleon.es/10.3389/fonc.2020.609056.

    Article  PubMed  Google Scholar 

  25. Goldsher D, Litt AW, Pinto RS, Bannon KR, Kricheff II. Dural “tail” associated with meningiomas on Gd-DTPA-enhanced MR images: characteristics, differential diagnostic value, and possible implications for treatment. Radiology. 1990;176(2):447–50. https://doiorg.publicaciones.saludcastillayleon.es/10.1148/radiology.176.2.2367659.

    Article  CAS  PubMed  Google Scholar 

  26. Takeuchi Y, Arakawa Y, Yokoo H, Mikami Y, Terada Y, Yoshida K, et al. Intra-cerebellar schwannoma with various degenerative changes: a case report and a systematic review. BMC Neurol. 2022;22(1):66. https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12883-022-02596-3.

    Article  PubMed  PubMed Central  Google Scholar 

  27. Majoie CB, Verbeeten B, Dol JA, Peeters FL. Trigeminal neuropathy: evaluation with MR imaging. Radiographics. 1995;15(4):795–811. https://doiorg.publicaciones.saludcastillayleon.es/10.1148/radiographics.15.4.7569130.

    Article  CAS  PubMed  Google Scholar 

  28. Ranabhat KS, Bishokarma P, Agrawal P, Shrestha R, Panth RK, Ghimire. Role of MR morphology and diffusion-weighted imaging in the evaluation of meningiomas: radio-pathologic correlation. JNMA J Nepal Med Assoc, 2019. 57(215): p. 37–44. https://doiorg.publicaciones.saludcastillayleon.es/10.31729/jnma.3968.

  29. Jhaveri MD, KL, Salzman, AG Osborn. Diagnostic Imaging: Brain. 2015, Philadelphia, PA: Elsevier Health Sciences.

  30. Ginat DT, Mangla R, Yeaney G, Ekholm S. Diffusion-weighted imaging of skull lesions. J Neurol Surg B Skull Base. 2014;75(3):204–13. https://doiorg.publicaciones.saludcastillayleon.es/10.1055/s-0034-1371362.

    Article  PubMed  PubMed Central  Google Scholar 

  31. Steffen P, Beyer LS, McDonough R, Thaler C, Faizy T, Fiehler J, et al. Improved detectability of brain stem ischemia by combining axial and coronal diffusion-weighted imaging. Stroke. 2021;52(5):1843–6. https://doiorg.publicaciones.saludcastillayleon.es/10.1161/STROKEAHA.120.032457.

    Article  PubMed  Google Scholar 

  32. Hakyemez B, Erdogan C, Bolca N, Yildirim N, Gokalp G, Parlak M. Evaluation of different cerebral mass lesions by perfusion-weighted MR imaging. J Magn Reson Imaging. 2006;24(4):817–24. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/jmri.20707.

    Article  PubMed  Google Scholar 

  33. Chanbour H, Jiblawi A, Taybah A, El Masri J, Jiblawi K. Trigeminal neuropathy ascribed to a probable intrinsic brainstem schwannoma of the pons: a case report. Cureus. 2021;13(10):e18764. https://doiorg.publicaciones.saludcastillayleon.es/10.7759/cureus.18764.

    Article  PubMed  PubMed Central  Google Scholar 

  34. Chou CT, Liang JF. Trigeminal schwannoma presenting as atypical trigeminal neuralgia and masseter atrophy. Acta Neurol Taiwan. 2014;23(1):38–9.

    PubMed  Google Scholar 

  35. Yoshino T, Shinozuka K, Yokoyama K, Yamakawa A, Tonogi M. Trigeminal schwannoma presenting with masticatory muscle atrophy: a rare case report. Appl Sci. 2022;12(19):9919.

    Article  CAS  Google Scholar 

  36. Tryggvason G, Barnett A, Kim J, Soken H, Maley J, Hansen MR. Radiographic association of schwannomas with sensory ganglia. Otol Neurotol. 2012;33(7):1276–82. https://doiorg.publicaciones.saludcastillayleon.es/10.1097/MAO.0b013e318263d315.

    Article  PubMed  PubMed Central  Google Scholar 

  37. Patel VA, Polster SP, Abou-Al-Shaar H, Kalmar CL, Zenonos GA, Wang EW, et al. Trigeminal schwannoma: a retrospective analysis of endoscopic endonasal management, treatment outcomes, and neuropathic sequelae. J Neurol Surg B Skull Base. 2023;84(5):444–51. https://doiorg.publicaciones.saludcastillayleon.es/10.1055/s-0042-1755592.

    Article  PubMed  Google Scholar 

  38. Kato K, Tomura N, Takahashi S, Watarai J. Motor denervation of tumors of the head and neck: changes in MR appearance. Magn Reson Med Sci. 2002;1(3):157–64. https://doiorg.publicaciones.saludcastillayleon.es/10.2463/mrms.1.157.

    Article  PubMed  Google Scholar 

Download references

Acknowledgements

Not applicable.

Clinical trial number

Not applicable.

Funding

This study has received funding from Taipei Veterans General Hospital, Taiwan [V111B-032, V112B-007, V114C-034 (to CHW); V111C-028, V112C-059, V112D67-002-MY3-1, V113C-182, V112D67-002-MY3-2, V114C-061 , V112D67-002-MY3-3 (to FCC)], Veterans General Hospitals and University System of Taiwan Joint Research Program [VGHUST 110-G1-5–2 (to FCC)], National Science and Technology Council, Taiwan [NSTC 110–2314-B-075–005- and 111–2314-B-075–025-MY3 (to CHW) and 109–2314-B-075–036, 110–2314-B-075–032, 112–2314-B-075–066 and 113–2314-B-075–037 (to FCC)], Yen Tjing Ling Medical Foundation, Taiwan [CI-111–2, CI-112–2 (to CHW)], Professor Tsuen CHANG’s Scholarship Program from Medical Scholarship Foundation In Memory Of Professor Albert Ly-Young Shen (to CHW and TML), Vivian W. Yen Neurological Foundation (to CHW and FCC) and Yin Shu-Tien Foundation Taipei Veterans General Hospital-National Yang Ming Chiao Tung University Excellent Physician Scientists Cultivation Program, [No.112-V-B-039; No. 113-V-B-020 (to CHW)].

Author information

Authors and Affiliations

  1. Department of Radiology, Taipei Veterans General Hospital, Taipei, Taiwan

    Yuan-Yu Tu, Hsin-Wei Wu, Fu-Sheng Hsueh, Wei-An Tai, Kai-Wei Yu, Chia-Hung Wu, Te-Ming Lin, Chung-Han Yang, Shu-Ting Chen & Feng-Chi Chang

  2. School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan

    Chia-Hung Wu & Feng-Chi Chang

Authors
  1. Yuan-Yu Tu
    View author publications

    You can also search for this author inPubMed Google Scholar

  2. Hsin-Wei Wu
    View author publications

    You can also search for this author inPubMed Google Scholar

  3. Fu-Sheng Hsueh
    View author publications

    You can also search for this author inPubMed Google Scholar

  4. Wei-An Tai
    View author publications

    You can also search for this author inPubMed Google Scholar

  5. Kai-Wei Yu
    View author publications

    You can also search for this author inPubMed Google Scholar

  6. Chia-Hung Wu
    View author publications

    You can also search for this author inPubMed Google Scholar

  7. Te-Ming Lin
    View author publications

    You can also search for this author inPubMed Google Scholar

  8. Chung-Han Yang
    View author publications

    You can also search for this author inPubMed Google Scholar

  9. Shu-Ting Chen
    View author publications

    You can also search for this author inPubMed Google Scholar

  10. Feng-Chi Chang
    View author publications

    You can also search for this author inPubMed Google Scholar

Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Yuan-Yu Tu and Hsin-Wei Wu. The first draft of the manuscript was written by Yuan-Yu Tu and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Feng-Chi Chang.

Ethics declarations

Ethics approval and consent to participate

The study was approved by the Institutional Review Board of Taipei Veterans General Hospital and conducted in adherence to the principles of the Declaration of Helsinki. Given the retrospective design of the study, the requirement for informed consent was waived.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Tu, YY., Wu, HW., Hsueh, FS. et al. MRI findings for the pretreatment diagnosis of small Meckel’s cave tumors: comparison of meningiomas and schwannomas. BMC Med Imaging 25, 57 (2025). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12880-025-01597-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12880-025-01597-1

Keywords

BMC Medical Imaging

ISSN: 1471-2342

Contact us