Combined open maxillectomy and endoscopic endonasal resection of a giant V2 trigeminal schwannoma.

BACKGROUND: Trigeminal schwannoma is a rare type of tumor that arises from the Schwann cells of the trigeminal nerve. METHOD: We present a case of a patient with a giant V2 trigeminal schwannoma with painful swelling in the left maxilla. A complete resection using a combined open maxillectomy and endoscopic endonasal approach was performed. CONCLUSION: This case highlights the importance of a multidisciplinary approach to perform a combined open and endoscopic approach for safe resection while preserving adequate speech and swallowing.

Preservation of cranial nerve function in large and giant trigeminal schwannoma resection: a case series.

BACKGROUND: Trigeminal schwannomas (TSs) are intracranial tumors that can cause significant brainstem compression. TS resection can be challenging because of the risk of new neurologic and cranial nerve deficits, especially with large (≥ 3 cm) or giant (≥ 4 cm) TSs. As prior surgical series include TSs of all sizes, we herein present our clinical experience treating large and giant TSs via microsurgical resection. METHODS: This was a retrospective, single-surgeon case series of adult patients with large or giant TSs treated with microsurgery in 2012-2023. RESULTS: Seven patients underwent microsurgical resection for TSs (1 large, 6 giant; 4 males; mean age 39 ± 14 years). Tumors were classified as type M (middle fossa in the interdural space; 1 case, 14%), type ME (middle fossa with extracranial extension; 3 cases, 43%), type MP (middle and posterior fossae; 2 cases, 29%), or type MPE (middle/posterior fossae and extracranial space; 1 case, 14%). Six patients were treated with a frontotemporal approach (combined with transmastoid craniotomy in the same sitting in one patient and a delayed transmaxillary approach in another), and one patient was treated using an orbitofrontotemporal approach. Gross total resection was achieved in 5 cases (2 near-total resections). Five patients had preoperative facial numbness, and 6 had immediate postoperative facial numbness, including two with worsened or new symptoms. Two patients (28%) demonstrated new non-trigeminal cranial nerve deficits over mean follow-up of 22 months. Overall, 80% of patients with preoperative facial numbness and 83% with facial numbness at any point experienced improvement or resolution during their postoperative course. All patients with preoperative or new postoperative non-trigeminal tumor-related cranial nerve deficits (4/4) experienced improvement or resolution on follow-up. One patient experienced tumor recurrence that has been managed conservatively. CONCLUSIONS: Microsurgical resection of large or giant TSs can be performed with low morbidity and excellent long-term cranial nerve function.

Nonpainful Trigeminal Neuropathy Associated with a Solitary Pontine Lesion: A Case Series.

A solitary pontine lesion (SPL) is a single brainstem lesion on the trigeminal nerve pathway without any other central nervous system lesion. This research aimed to investigate the demographic and clinical features of nonpainful TNO patients with SPL and identify the most frequently affected anatomical areas using lesion mapping techniques. Demographic and clinical features were retrospectively reviewed from the patients' charts. Brain lesions were mapped using MRIcroGL software. The study included 6 patients (three females and three males) with an SPL. The median age of the patients was 57 (range: 46-68) years. Cranial MRI displayed lesions in the dorsolateral pons and the cerebellar peduncle. The lesion mapping revealed that the lesions were on the trigeminal nerve pathway. SPL is an uncommon cause of TNO. Nonpainful SPL patients have demographic, clinical, and radiological features similar to those of painful SPL patients. The lesion mapping showed that the same brainstem areas are affected in painful and nonpainful SPL patients.

Uncommon cause of trigeminal neuritis and central nervous system involvement by herpes labialis: a case report.

BACKGROUND: Trigeminal neuropathy is characterized by numbness in the region innervated by the trigeminal nerves, with or without neuropathic weakness in the muscles of mastication. Trigeminal neuritis is a form of trigeminal neuropathy in which the lesion is caused by an inflammation. Herein, we report a patient with trigeminal neuritis due to central nervous system (CNS) involvement of herpes labialis (HL) infection, which was successfully treated with anti-viral and anti-inflammatory agents. CASE PRESENTATION: A young healthy female presented with numbness in the left hemiface for two weeks. She had a preceding typical HL infection on left facial lip one week before the sensory symptom onset. Brain magnetic resonance imaging revealed high signal intensities and asymmetrical thickening with enhancement along the cisternal segment of the left trigeminal nerve. Additionally, brain MR angiography showed multifocal stenoses in the M1 segment of the middle cerebral artery and the cavernous portion of the internal carotid artery. Cerebrospinal fluid (CSF) examination showed mild pleocytosis with normal protein level, glucose ratio, but CSF polymerase chain reaction assay for specific anti-viral antibodies including herpes simplex virus was negative, and CSF culture also did not identify a specific pathogen. The results of serologic testing including tumor markers and autoimmune markers were all unremarkable. A tentative diagnosis of trigeminal neuritis as a complication of HL involving the CNS was made considering the clinical, neuroradiological, and laboratory findings of the patient. Therefore, the patient was treated with intravenous methylprednisolone and acyclovir for 10 days. After the treatments, her sensory disturbance was markedly improved. Brain MRI at the 3-month follow-up also demonstrated improvement of previously identified high signal intensity lesions and multifocal intracerebral artery stenoses. CONCLUSION: HL is usually a self-limiting, benign disease without complications, but rarely presents as trigeminal neuritis due to CNS involvement. Therefore, meticulous evaluation may be necessary if trigeminal neuritis or CNS involving symptoms occur after HL.

Recombinant Human Nerve Growth Factor for Pediatric Neurotrophic Keratopathy.

ABSTRACT: A 4-year-old boy presented with right neurotrophic corneal ulcer, lagophthalmos, and facial palsy 8 months after neurosurgery for synchronous brain tumors. Initial treatment with topical antibiotics, topical corticosteroids, lubrication, and lateral tarsorrhaphy successfully treated the corneal epithelial defect; however, the cornea continued to demonstrate diffuse epitheliopathy and a dense stromal opacity and remained insensate on Cochet-Bonnet esthesiometry. After a course of topical cenegermin, central corneal sensation normalized, and the corneal epitheliopathy was markedly improved. Two years after the completion of cenegermin, corneal sensation was maintained; there were no recurrences of epithelial defects, and the stromal opacity had markedly improved. In vivo confocal microscopy (IVCM) demonstrated the presence of subbasal corneal innervation. This report highlights the safety and prolonged effects of cenegermin for the treatment of pediatric iatrogenic neurotrophic keratopathy, as evidenced by the clinical course and IVCM.

Cutting Edge: Topical Recombinant Nerve Growth Factor for the Treatment of Neurotrophic Keratopathy-Biologicals as a Novel Therapy for Neurotrophic Keratopathy.

ABSTRACT: Ophthalmologists find management of neurotrophic keratopathy (NK) challenging because conventional therapy lacks efficacy and may result in permanent loss of vision. Recombinant nerve growth factor (cenegermin) targets the underlying pathogenesis of NK by regenerating corneal nerves and healing the corneal epithelium through promotion of proliferation, maturing corneal epithelial cells. It has been approved as Food Drug Association-approved treatment of NK. In this article, the background, clinical trials, and impact of recombinant nerve growth factor as the first neurotrophic factor for the restoration of corneal integrity, homeostasis, and corneal nerve regeneration are discussed.

Trigeminal neuropathy causes hypomyelination in the anterior cingulate cortex, disrupts the synchrony of neural circuitry, and impairs decision-making in male rats.

Infraorbital nerve-chronic constriction injury (ION-CCI) has become the most popular chronic trigeminal neuropathic pain (TNP) injury animal model which causes prolonged mechanical allodynia. Accumulative evidence suggests that TNP interferes with cognitive functions, however the underlying mechanisms are not known. The aim of this study was to investigate decision-making performance as well as synaptic and large-scale neural synchronized alterations in the spinal trigeminal nucleus (SpV) circuitry and anterior cingulate cortex (ACC) neural circuitry in male rats with TNP. Rat gambling task showed that ION-CCI led to decrease the proportion of good decision makers and increase the proportion of poor decision makers. Electrophysiological recordings showed long-lasting synaptic potentiation of local field potential in the trigeminal ganglia-SpV caudalis (SpVc) synapses in TNP rats. In this study, TNP led to disruption of ACC spike timing and basolateral amygdala (BLA) theta oscillation associated with suppressed synchronization of theta oscillation between the BLA and ACC, indicating reduced neuronal communications. Myelination is critical for information flow between brain regions, and myelin plasticity is an important feature for learning. Neural activity in the cortical regions impacts myelination by regulating oligodendrocyte (OL) proliferation, differentiation, and myelin formation. We characterized newly formed oligodendrocyte progenitor cells, and mature OLs are reduced in TNP and are associated with reduced myelin strength in the ACC region. The functional disturbances in the BLA-ACC neural circuitry is pathologically associated with the myelin defects in the ACC region which may be relevant causes for the deficits in decision-making in chronic TNP state.

Pseudomonas aeruginosa-induced nociceptor activation increases susceptibility to infection.

We report a rapid reduction in blink reflexes during in vivo ocular Pseudomonas aeruginosa infection, which is commonly attributed and indicative of functional neuronal damage. Sensory neurons derived in vitro from trigeminal ganglia (TG) were able to directly respond to P. aeruginosa but reacted significantly less to strains of P. aeruginosa that lacked virulence factors such as pili, flagella, or a type III secretion system. These observations led us to explore the impact of neurons on the host's susceptibility to P. aeruginosa keratitis. Mice were treated with Resiniferatoxin (RTX), a potent activator of Transient Receptor Potential Vanilloid 1 (TRPV1) channels, which significantly ablated corneal sensory neurons, exhibited delayed disease progression that was exemplified with decreased bacterial corneal burdens and altered neutrophil trafficking. Sensitization to disease was due to the increased frequencies of CGRP-induced ICAM-1+ neutrophils in the infected corneas and reduced neutrophil bactericidal activities. These data showed that sensory neurons regulate corneal neutrophil responses in a tissue-specific matter affecting disease progression during P. aeruginosa keratitis. Hence, therapeutic modalities that control nociception could beneficially impact anti-infective therapy.

Multicompartmental Epidermoid Cyst Causing Chronic Parotid Gland and Masticator Space Muscle Atrophy.

Epidermoid cysts are rare benign intracranial tumors of congenital origin. They are slow-growing and are seen to insinuate between brain structures. These are commonly located in cerebello-pontine angle and parasellar regions. The symptoms produced are primarily due to mass effect. Hearing loss, facial nerve palsy, and trigeminal neuralgia are reported when cranial nerves are involved; motor palsy of trigeminal nerve is uncommon. Here, we present an interesting case of an extensive multicompartmental epidermoid cyst causing atrophy of trigeminal nerve with radiologic evidence of chronic motor trigeminal nerve palsy characterized by atrophy of masticator space muscles and parotid gland.

Single-stage endoscopic endonasal approach for the complete removal of trigeminal schwannomas occupying both the middle and posterior fossae.

To introduce a purely endoscopic endonasal trans-Meckel's cave approach or a transclival approach for trigeminal schwannomas (TSs) involving both the middle and posterior fossae. This retrospective study reviewed the medical records and intraoperative videos of 8 patients with TSs occupying both the middle and posterior fossae who underwent an endoscopic endonasal approach (EEA) between January 2017 and October 2019. All 8 patients received total resection under a single-stage EEA. Six patients underwent endoscopic endonasal resection via a purely trans-Meckel's cave approach, and 2 patients underwent endoscopic endonasal resection via a trans-Meckel's cave approach combined with a transclival approach. There was no surgical-related hemorrhage or mortality and no cerebrospinal fluid leakage. All headache symptoms completely improved postoperatively (n = 3 patients). All cranial nerve (CN) symptoms (CN IX and CN VI) improved postoperatively. The most common preoperative symptom was facial numbness (n = 5 patients); 2 of these 5 patients showed a partial improvement, 1 patient experienced worsening, and 2 patients remained unchanged at the last follow-up. Four patients developed postoperative complications, including CN VI palsy (n = 2), dry eye (n = 2), mastication weakness (n = 1), and facial numbness (n = 2). All complications except for dry eye were relieved at the last follow-up, but the patients with dry eye did not develop corneal keratopathy. The endoscopic endonasal trans-Meckel's cave and transclival approaches provide adequate exposure and improve the rate of total resection for TSs occupying both the middle and posterior fossae with minimal invasion. It may be possible to use these approaches as a safe alternative to conventional surgical approaches.

Epidermoid Cyst Extending Along Trigeminal Nerve Pathway with Unusual Imaging Findings.

Epidermoid cysts (ECs) are benign extraaxial tumors. They frequently occur at the cerebellopontine angle and parasellar regions. However, they rarely occur in the Meckel's cave. Typically, ECs appear as a hypointense mass on T1-weighted magnetic resonance imaging (MRI) and hyperintense on T2-weighted MRI. However, ECs may occasionally present as hyperintense on T1-weighted imaging and hypointense on T2-weighted imaging. When this occurs, they are known as white epidermoid cysts. We present a case of a 25-year-old woman with a 3-month history of hypoesthesia in the distribution of the right trigeminal nerve. MRI showed a lesion located within the Meckel's cave. The MRI signal was heterogeneous, with hyperintense areas on T1-weighted images, being hypointense on T2-weighted imaging. Preoperative suspicion was trigeminal schwannoma with unusual radiologic features. Finally, the pathologic diagnosis was epidermoid cyst. Therefore to establish a proper preoperative diagnosis, one should be aware that ECs can occur in Meckel's cave and with unusual radiologic features, as occurred in the case described earlier.

"Apoplectic" Recurrence of Massive Trigeminal Neurinomas: Report of 7 Cases.

OBJECTIVE: The pattern of recurrence of large trigeminal neurinomas is analyzed on the basis of experience with 7 cases. METHODS: This is a report of 7 cases of large trigeminal neurinomas that were operated on an average of 11 years earlier. After being relatively asymptomatic over the years, these patients worsened relatively suddenly in their neurologic symptoms and were reoperated. RESULTS: Imaging showed massive recurrence with tumor having cystic and solid components with sizes ranging from 4.5-11 cm. In 4 cases, the cysts at the time of initial presentation and at the time of recurrence showed a well-defined fluid level within the fluid content of the cyst. During operation it was seen that the tumor contained "hemorrhagic" fluid that was under significant pressure. The solid component in the circumferential periphery of the cyst fluid was soft, necrotic, and vascular. The entire recurrence in the middle and posterior cranial fossa and in the extracranial compartment was "interdural" or within the dural confines. Radical tumor resection within the dural confines by deploying relatively small surgical exposure resulted in "unusually" rapid recovery in the symptoms. Histological examination of the tumor did not reveal any malignant transformation. CONCLUSIONS: The cases add further insight to the growth pattern and characteristics of large trigeminal neurinomas.

Optic, trigeminal, and facial neuropathy related to anti-neurofascin 155 antibody.

OBJECTIVE: To characterize the frequency and patterns of optic, trigeminal, and facial nerve involvement by neuroimaging and electrophysiology in IgG4 anti-neurofascin 155 antibody-positive (NF155+ ) chronic inflammatory demyelinating polyneuropathy (CIDP). METHODS: Thirteen IgG4 NF155+ CIDP patients with mean onset age of 34 years (11 men) were subjected to neurological examination, blink reflex, and visual-evoked potential (VEP) testing, and axial and/or coronal T2-weighted head magnetic resonance imaging (MRI). RESULTS: Among 13 patients, facial sensory impairment, facial weakness, and apparent visual impairment were observed in three (23.1%), two (15.4%), and two (15.4%) patients, respectively. All 12 patients tested had blink reflex abnormalities: absent and/or delayed R1 in 11 (91.7%), and absent and/or delayed R2 in 10 (83.3%). R1 latencies had strong positive correlations with serum anti-NF155 antibody levels (r = 0.9, P ≤ 0.0001 on both sides) and distal and F wave latencies of the median and ulnar nerves. Absent and/or prolonged VEPs were observed in 10/13 (76.9%) patients and 17/26 (65.4%) eyes. On MRI, hypertrophy, and high signal intensity of trigeminal nerves were detected in 9/13 (69.2%) and 10/13 (76.9%) patients, respectively, whereas optic nerves were normal in all patients. The intra-orbital trigeminal nerve width on coronal sections showed a significant positive correlation with disease duration. INTERPRETATION: Subclinical demyelination frequently occurs in the optic, trigeminal, and facial nerves in IgG4 NF155+ CIDP, suggesting that both central and peripheral myelin structures of the cranial nerves are involved in this condition, whereas nerve hypertrophy only develops in myelinated peripheral nerve fibers.

Neuroaxonal Degeneration in Patients With Multiple Sclerosis: An Optical Coherence Tomography and in Vivo Corneal Confocal Microscopy Study.

PURPOSE: To investigate the effect of multiple sclerosis (MS) on corneal and retinal nerve fiber by quantifying corneal subbasal nerve fibers and retinal ganglion cells. METHODS: A total of 46 eyes of 23 patients with MS and 42 eyes of 21 healthy subjects were included in the study. All patients and healthy subjects underwent a comprehensive ocular examination. In vivo confocal microscopy with Heidelberg Retina Tomograph in association with Rostock Cornea Module (Heidelberg Engineering, Heidelberg, Germany) and a swept-source optical coherence tomography (Topcon Corporation) were performed in all patients and healthy subjects. The number of subbasal nerve fibers and the nerve fiber density were calculated. Student t test was used to compare eyes with MS with control eyes. The normal distribution was first confirmed with the Shapiro-Wilk test. RESULTS: A statistically significant (P < 0.05) decrease was found for nerve fiber number, ganglion cell-inner plexiform layer, and retinal nerve fiber layer in patients with MS compared with those of healthy subjects. Moreover, an inverse correlation was found between retinal nerve fiber layer (r = -0.32), nerve fiber number (r = -0.47), and ganglion cell-inner plexiform layer (r = -0.51) and Expanded Disability Status Scale. A direct correlation between Expanded Disability Status Scale and optic neuritis frequency was found (r = 0.322). CONCLUSIONS: In vivo confocal microscopy showed a difference in corneal morphological parameters and retinal damage; moreover, these changes seemed to be related to the degree of neurological disability. Both retinal ganglion and trigeminal cell atrophy measurements could become affordable and accessible biomarkers for clinical trials in progressive disease.

Diabetic Neuropathy Is Characterized by Progressive Corneal Nerve Fiber Loss in the Central and Inferior Whorl Regions.

Purpose: We hypothesized that longitudinal changes in corneal nerve morphology would differ between the central cornea and inferior whorl in relation to other measures of diabetic neuropathy. Methods: Thirty patients with diabetes (age: 54.08 ± 15.86, duration: 23.95 ± 14.2, HbA1c: 7.51 ± 1.37) and 19 age-matched healthy controls (age: 49.47 ± 13.25) underwent assessment of neuropathy disability score (NDS), vibration perception threshold (VPT), cold (CPT) and warm (WPT) perception thresholds, peroneal motor nerve conduction velocity (PMNCV), corneal nerve fiber density (CNFD), branch density (CNBD), fiber length (CNFL), inferior whorl length (IWL), and the average of CNFL and IWL (ANFL) at baseline and after 1 to 8 years. Results: In patients with diabetes, between baseline and follow-up, there was a significant reduction in CNBD (57.72 ± 30.08 vs. 44.04 ± 23.69; P = 0.02), CNFL (21.77 ± 5.19 vs. 15.65 ± 4.7; P < 0.0001), IWL (24.69 ± 8.67 vs. 14.23 ± 6.13; P < 0.0001), ANFL (23.26 ± 5.53 vs. 15.09 ± 4.48; P < 0.0001), and WPT (43.56 ± 4.43 vs. 40.78 ± 4.93; P = 0.01), and an increase in VPT (12.9 ± 8.96 vs. 13.78 ± 8.99; P = 0.02). There was no significant change in CNFD (27.12 ± 8.2 vs. 25.43 ± 7.11; P = 0.2), NDS (3.38 ± 3.35 vs. 2.61 ± 2.8; P = 0.08), CPT (17.7 ± 10.59 vs. 22.45 ± 9.23; P = 0.06), or PMNCV (42.4 ± 4.21 vs. 42.16 ± 6.3; P = 0.2). Conclusions: There is evidence of corneal nerve loss in patients with diabetes, particularly at the inferior whorl during follow-up.

Diagnostic Values of Clinical and Magnetic Resonance Findings in Presumptive Trigeminal Neuropathy: 49 Dogs.

The goal of this retrospective, cross-sectional study was to describe the different etiologies of trigeminal neuropathy based on clinical and MRI findings and to evaluate the significance of associated concomitant disorders. MRI studies of 49 dogs with trigeminal neuropathy were blindly reviewed and were classified into the following three groups: neoplasia, neuritis, or idiopathic trigeminal neuropathy (ITN). Thirty-one percent were suspected to have neoplasia (all unilateral), 16% to have neuritis (1 bilateral and 7 unilateral), and 53% to have ITN (4 unilateral and 22 bilateral). Dogs with clinical bilateral trigeminal dysfunction were most likely to have a diagnosis of ITN (predicted probability 95.7%). Unilateral clinical signs were significantly associated with neoplasia or neuritis compared with ITN (P < .001 and P = .002, respectively). Even with marked brainstem neoplastic involvement, central neurological deficits may be absent. Sensory impairment was significantly associated with either neoplasia or neuritis compared with ITN (P = .007 and P = .03, respectively). Ipsilateral noninfectious middle ear effusion was only seen in dogs with neoplasia (33%). Horner's syndrome was present in 12% of all dogs (2 dogs in each group). Dogs with neoplasia were significantly older than dogs with neuritis (P = .02) and ITN (P = .002). JAAHA-MS-6997.

Endoscopic transorbital and endonasal approach for trigeminal schwannomas: a retrospective multicenter analysis (KOSEN-005).

OBJECTIVE: Trigeminal schwannomas are rare neoplasms with an incidence of less than 1% that require a comprehensive surgical strategy. These tumors can occur anywhere along the path of the trigeminal nerve, capable of extending intradurally into the middle and posterior fossae, and extracranially into the orbital, pterygopalatine, and infratemporal fossa. Recent advancements in endoscopic surgery have suggested a more minimally invasive and direct route for tumors in and around Meckel's cave, including the endoscopic endonasal approach (EEA) and endoscopic transorbital superior eyelid approach (ETOA). The authors assess the feasibility and outcomes of EEA and ETOA for trigeminal schwannomas. METHODS: A retrospective multicenter analysis was performed on 25 patients who underwent endoscopic surgical treatment for trigeminal schwannomas between September 2011 and February 2019. Thirteen patients (52%) underwent EEA and 12 (48%) had ETOA, one of whom underwent a combined approach with retrosigmoid craniotomy. The extent of resection, clinical outcome, and surgical morbidity were analyzed to evaluate the feasibility and selection of surgical approach between EEA and ETOA based on predominant location of trigeminal schwannomas. RESULTS: According to predominant tumor location, 9 patients (36%) had middle fossa tumors (Samii type A), 8 patients (32%) had dumbbell-shaped tumors located in the middle and posterior cranial fossae (Samii type C), and another 8 patients (32%) had extracranial tumors (Samii type D). Gross-total resection (GTR, n = 12) and near-total resection (NTR, n = 7) were achieved in 19 patients (76%). The GTR/NTR rates were 81.8% for ETOA and 69.2% for EEA. The GTR/NTR rates of ETOA and EEA according to the classifications were 100% and 50% for tumors confined to the middle cranial fossa, 75% and 33% for dumbbell-shaped tumors located in the middle and posterior cranial fossae, and 50% and 100% for extracranial tumors. There were no postoperative CSF leaks. The most common preoperative symptom was trigeminal sensory dysfunction, which improved in 15 of 21 patients (71.4%). Three patients experienced new postoperative complications such as vasospasm (n = 1), wound infection (n = 1), and medial gaze palsy (n = 1). CONCLUSIONS: ETOA provides adequate access and resectability for trigeminal schwannomas limited in the middle fossa or dumbbell-shaped tumors located in the middle and posterior fossae, as does EEA for extracranial tumors. Tumors predominantly involving the posterior fossa still remain a challenge in endoscopic surgery.

Hypertrophic Interstitial Neuropathy of the Trigeminal Nerve: Case Report and Literature Review.

BACKGROUND AND IMPORTANCE: Hypertrophic interstitial neuropathy (HIN) is an uncommon, non-neoplastic lesion typically affecting peripheral nerves. Cranial nerve (CN) involvement is exceedingly rare. We present a case of isolated trigeminal nerve HIN manifesting with V3 distribution neuralgia. CLINICAL PRESENTATION: A 50-yr-old male presented with left sided trigeminal neuralgia refractory to medical management. The patient underwent retromastoid craniectomy for possible microvascular decompression. Intra-operatively, the trigeminal nerve appeared to be focally enlarged with a sausage-like configuration. We selectively resected 1 fascicle which was predominantly involved. Histopathological examination revealed onion bulb formations composed of Schwann cells around centrally placed axons. A diagnosis of HIN was made. Postoperatively, the patient experienced complete resolution of symptoms. CONCLUSION: This is the third case of isolated trigeminal nerve HIN in the literature. We performed a selective resection in a patient presenting with trigeminal neuralgia, resulting in complete resolution of symptoms. It is reported here with intraoperative microscope images, along with a review and analysis of this topic as it related to CN.