Three Cases of Trigeminal Neuralgia with Radiographic Absence of Meckel's Cave

Multi-metric predictors of radiofrequency-treated trigeminal neuralgias

Evaluation of neurovascular compression-related trigeminal neuralgia (NVC-TN) and its resolution through microvascular decompression are demonstrable by MRI and intraoperatively [Leal et al. (Atrophic changes in the trigeminal nerves of patients with trigeminal neuralgia due to neurovascular compression and their association with the severity of compression and clinical outcomes: Clinical article. J Neurosurg. 2014;120(6):1484-1495)]. Non-NVC-TNs treated by radiofrequency (RF) lack such detectable features. Multimodal integration of pre-surgical diffusion tensor imaging (DTI) and volumetry (VOL) with intraoperative neurophysiology (ION) could improve understanding and performance of RF among non-NVC-TN. We hypothesized that DTI disturbances' localization (central relay versus peripherally) rather than their values bares the most significant predictive value upon outcome and that ION could quantitatively both localize and assist RF of affected branches. The first pre-surgical step evaluated the differences between affected and non-affected sides (by DTI and VOL). Four TN's segments were studied, from peripheral to central relay: Meckel's cave-trigeminal ganglion (MC-TGN), cisternal portion, root entry zone (REZ) and spinal tract [Lin et al. (Flatness of the Meckel cave may cause primary trigeminal neuralgia: A radiomics-based study. J Headache Pain. 2021;22(1):104)]. In the second intraoperative step, we used both ION and patient's testimonies to confirm the localization of the affected branch, evolving hypoesthesia, pain reduction and monitoring of adverse effects [Sindou (Neurophysiological navigation in the trigeminal nerve: Use of masticatory responses and facial motor responses evoked by electrical stimulation of the trigeminal rootlets for RF-thermorhizotomy guidance. Stereotact Funct Neurosurg. 1999;73(1-4):117-121); Sindou and Tatli (Traitement de la névralgie trigéminale par thermorhizotomie. Neurochirurgie. 2009;55(2):203-210)]. Last and postoperatively, each data set's features and correlation with short-term (3 months) and long-term outcomes (23.5 ± 6.7 months) were independently analysed and blind to each other. Finally, we designed a multimodal predictive model. Sixteen non-NVC-TN patients (mean 53.6 ± SD years old) with mean duration of 6.56 ± 4.1 years (75% right TN; 43.8% V3) were included. After 23.5 ± 6.7 months, 14/16 were good responders. Age, gender, TN duration and side/branch did not correlate with outcomes. Affected sides showed significant DTI disturbances in both peripheral (MC-TGNs) and central-relay (REZ) segments. However, worse outcome correlated only with REZ-located DTI disturbances (P = 0.04; r = 0.53). Concerning volumetry, affected MC-TGNs were abnormally flatter: lower volumes and surface area correlated with worse outcomes (both P = 0.033; r = 0.55 and 0.77, respectively). Intraoperatively, ION could not differ the affected from non-affected branch. However, the magnitude of ION's amplitude reduction (ION-Δ-Amplitude) had the most significant correlation with outcomes (r = 0.86; P < 0.00006). It was higher among responders [68.4% (50-82%)], and a <40% reduction characterized non-responders [36.7% (0-40%)]. Multiple regression showed that ION-Δ-Amplitude, centrally located only REZ DTI integrity and MC-TGN flatness explain 82.2% of the variance of post-RF visual analogue score. Integration of pre-surgical DTI-VOL with ION-Δ-Amplitude suggests a multi-metric predictive model of post-RF outcome in non-NVC-TN. In multiple regression, central-relay REZ DTI disturbances and insufficiently reduced excitability (<40%) predicted worse outcome. Quantitative fine-tuned ION tools should be sought for peri-operative evaluation of the affected branches.

Absent Meckel's cave as a possible cause of trigeminal neuralgia: A case report

Trigeminal neuralgia (TN) is a debilitating yet potentially treatable facial pain disorder.TN is difficult to miss clinically, as patients' clinical presentation is often strikingly stereotypical: unilateral, paroxysmal, stimulus-dependent pain involving the trigeminal territory. Magnetic resonance imaging (MRI), which is used for further evaluation of an underlying etiology of TN, most commonly shows neurovascular compression of the trigeminal nerve to be the culprit. Secondary etiologies, though less common, do exist. An absent Meckel's cave with ipsilateral TN was reported in a few case reports and series, and whether an etiological relationship exists is yet to be established. We herein present a case of a 22-year-old female patient who presented with typical TN clinical manifestations. MRI was ordered to assess for the underlying cause and an ipsilateral absent Meckel's cave was the only significant finding. This case report adds to the scarcity of literature highlighting this entity, further larger clinical studies are needed to establish a causal relationship.

Absence of Meckel's Cave with Trigeminal Neuralgia: A Case Report

Trigeminal neuralgia (TN) is a disabling painful condition along the course of the sensory distribution of the trigeminal nerve that most commonly occurs due to vascular compression or conflict at the root entry zone of the trigeminal nerve. We report a 27-year-old female patient who presented with pain and an electric shock-like sensation on the right side of her face that started three years ago. Magnetic resonance imaging of the brain was done and revealed no neurovascular conflict along the course of the trigeminal nerve. The absence of Meckel's cave with atrophy of the cisternal segment of the trigeminal nerve on the affected side was reported. The absence of Meckel's cave is an exceedingly rare cause of TN, and only a handful of reported cases in the literature suggest the association between them.

Flatness of the Meckel cave may cause primary trigeminal neuralgia: a radiomics-based study

Background

Neurovascular contact (NVC) is the main cause of primary trigeminal neuralgia (PTN); however, cases of PTN without NVC are still observed. In this study, the Meckel cave (MC) morphology in PTN were analyzed by radiomics and compared to healthy controls (HCs) to explore the cause of PTN.

Methods

We studied the 3.0T MRI data of 115 patients with PTN and 46 HCs. Bilateral MC was modeled using the 3D Slicer software, and the morphological characteristics of MC were analyzed using the radiomics method.

Results

The right side incidence rate in the PTN group was higher than the left side incidence. By analyzing the flatness feature of MC, we observed that the affected side of the PTN was lower than that of the unaffected side, the right MC of the PTN and HC was lower than that of the left MC, the MC of the affected side of the left and right PTN without bilateral NVC was lower than that of the unaffected side.

Conclusions

By providing a method to analyze the morphology of the MC, we found that there is an asymmetry in the morphology of bilateral MC in the PTN and HC groups. It can be inferred that the flatness of the MC may be a cause of PTN.

Meckel Cave: An Anatomical Study Using Magnetic Resonance Imaging

OBJECTIVE

To our knowledge, few studies have investigated anatomy of the Meckel cave with neuroimaging modalities. The present study aimed to characterize it using magnetic resonance imaging (MRI).

PATIENTS AND METHODS

Following conventional MRI examination, a total of 101 patients underwent T2-weighted imaging in thin-sliced coronal and sagittal sections, and 11 patients underwent constructive interference steady-state sequences in thin-sliced sagittal sections. Moreover, 3 injected cadaver heads were dissected.

RESULTS

In the cadaver specimens, the size and extent of the cerebrospinal fluid-filled space between the Gasserian ganglion and surrounding arachnoids were difficult to define. On the T2-weighted imaging, the Meckel cave was delineated with variable morphologies and left-right asymmetry. On the sagittal images, the shape of the Meckel cave could be classified into 3 different types, bulbous, oval, and flat, with the oval being the most frequent that comprised 60%. Furthermore, on the sagittal constructive interference steady-state images, parts of the trigeminal nerve distributed in the Meckel cave were delineated in all patients. The ophthalmic, maxillary, and mandibular divisions were clearly distinguished on both sides.

CONCLUSIONS

The Meckel cave is a structure characterized by diverse morphologies and left-right asymmetry. Thin-sliced T2-weighted imaging is useful for exploring the anatomy of the Meckel cave.

Absence of Meckel Cave: A Rare Cause of Trigeminal Neuralgia

Trigeminal neuralgia is a debilitating condition with numerous etiologies. In this retrospective case series, we report a cohort of patients with a rarely described entity, absence of Meckel cave, and propose this as a rare cause of trigeminal neuralgia. A search of the electronic medical record was performed between 2000 and 2020 to identify MR imaging reports with terms including "Meckel's cave" and "hypoplasia," "atresia," "collapse," or "asymmetry." Images were reviewed by 2 blinded, board-certified neuroradiologists. Seven cases of the absence of Meckel cave were identified. Seven patients (100%) had ipsilateral trigeminal neuralgia and ipsilateral trigeminal nerve atrophy, suggesting an association between absence of Meckel cave and trigeminal neuralgia. Absence of Meckel cave is a rare entity of unknown etiology, with few existing reports that suggest the possibility of an association with trigeminal neuralgia. Its recognition may have important implications in patient management. Future studies and longitudinal data are needed to assess treatment outcomes and added risks from surgical intervention in these patients.