Periodic abducens nerve palsy in adults caused by neurovascular compression

Abducens Nerve Palsy Due to Neurovascular Compression

BACKGROUND

Neurovascular compression (NVC) as the cause of abducens nerve palsy is an infrequent event. Only a small number of cases have been reported in the literature, and the efficacy of microvascular decompression (MVD) for abducens nerve palsy remains unclear.

METHODS

We reviewed previously reported cases of abducens nerve palsy caused by NVC and added our own cases. We analyzed the clinical characteristics of vascular compression abducens nerve palsy and assessed the indication for MVD.

RESULTS

Twenty-two patients with isolated abducens nerve palsy due to vascular compression were confirmed in total, consisting of 20 patients (19 publications) from the literature search and 2 cases from our experienced cases. All patients had no possible causes for isolated abducens nerve palsy except the NVC on the nerve root. Unlike the sudden onset in the typical abducens nerve palsy, all patients demonstrated gradual development of the symptom in NVC-related abducens palsy. Careful observation was the most common strategy in most patients; however, no noticeable improvement was reported in the conservative treatment. Surgical intervention was performed in 6 patients after observation for several months and showed favorable outcomes in all cases.

CONCLUSIONS

Vascular compression could be a potential cause of abducens nerve palsy. Gradual onset or episodic symptom of abducens palsy with a definitive radiological finding of vascular compression deserves considering MVD for abducens nerve palsy.

Vertebrobasilar dolichoectasia and other arterial abnormalities leading to abducens nerve palsy

INTRODUCTION

Dolichoectatic vessels can cause cranial nerve dysfunction by either direct compression or ischemia. Abducens nerve palsy due to neurovascular compression by elongated, enlarged, tortuous or dilated arteries is an uncommon but important cause.

AIM

To highlight neurovascular compression as a cause of abducens nerve palsy and discuss various diagnostic techniques.

METHODS

Manuscripts were identified using the National Institutes of Health PubMed literature search system. Search terms included abducens nerve palsy, neurovascular compression, dolichoectasia and arterial compression. Inclusion criteria required that the articles were written in English.

RESULTS

The literature search identified 21 case reports where abducens nerve palsy was due to vascular compression. Out of these 18 patients were male and the mean age was 54 years. Eight patients had unilateral right abducens nerve involvement; eleven patients had unilateral left nerve involvement and two patients had bilateral involvement. The arteries causing the compression were basilar, vertebral and anterior inferior cerebellar arteries. A compressed abducens nerve is not usually clearly detected on CT (Computed Tomography) or MRI (Magnetic Resonance Imaging). MRA (Magnetic Resonance Angiography), Heavy T2- WI (weighted imaging), CISS (constructive interference in steady state) and FIESTA (Fast Imaging Employing Steady-state Acquisition) are essential to demonstrate vascular compression of the abducens nerve. The various treatment options included controlling hypertension, glasses with prisms, muscle resection and microvascular decompression.

Location of the abducens nerve stretched by a tortuous vertebrobasilar artery in trigeminal neuralgia

BACKGROUND

Trigeminal neuralgia (TGN) caused by the vertebrobasilar artery (VBA) is uncommon. The abducens nerve root is frequently dislocated by a tortuous VBA near the trigeminal nerve root. This unusual location of the root is not well known. This study aimed to investigate the location of the stretched abducens nerve root.

METHODS

The objective is 26 patients with VBA-related TGN who underwent microvascular decompression (MVD). We retrospectively investigated the course of the abducens nerve root with magnetic resonance imaging (MRI) with three-dimensional (3D) imaging and surgical findings. The displacement of the abducens nerve root on the affected side was compared to the contralateral side.

RESULTS

The abducens nerve root was distorted by a tortuous VBA (46.2%) or the anterior inferior cerebellar artery (53.8%). The average length of the cisternal segment was stretched to 23.4 mm versus 12.4 mm on the contralateral side. The peak point of the elevated abducens nerve root was mostly located rostro-medial (65.4%) or caudo-medial (34.6%) to the neurovascular compression site of the trigeminal nerve with a mean distance of 9.1 mm. Contact with the trigeminal nerve root was observed in 7 patients (26.9%). Three-dimensional imaging was consistent with the surgical findings and useful in predicting the location of the abducens nerve root. No abducens nerve palsy was noted in our series.

CONCLUSIONS

The abducens nerve root is located near the trigeminal nerve root in VBA-related TGN. Preoperative understanding of the unusual course of the abducens nerve root contributes to avoiding accidental nerve injury during MVD.

Microvascular decompression for abducens nerve palsy due to neurovascular compression from both the vertebral artery and anterior inferior cerebellar artery: A case report

Background

Neurovascular compression is an extremely rare etiology of isolated abducens nerve palsy. We describe a successfully treated case of isolated abducens nerve palsy due to sandwich-type compression by the vertebral artery (VA) and anterior inferior cerebellar artery (AICA).

Case Description

A 30-year-old man presented with a 6-month history of horizontal diplopia without other symptoms. Magnetic resonance imaging (MRI) demonstrated pinching of the left abducens nerve between the elongated left VA and left AICA. MRI showed no abnormal findings in the brainstem, cavernous sinus, or orbit. Surgery was performed using a standard lateral suboccipital approach. The abducens nerve was found to be severely compressed from both sides by the VA and AICA, with marked indentation. First, the VA was transposed and fixed to the dura mater of the petrous bone using a Teflon sling with the dripping of fibrin glue. Next, because of limited mobilization due to penetration of the AICA into the nerve, the AICA transfixing the nerve was attached to the pons with Teflon felt and fibrin glue to move the AICA away from the main trunk of the abducens nerve. The abducens nerve palsy gradually improved and eventually resolved by 4 months after the operation.

Conclusion

When an elongated vertebrobasilar artery is identified as the offending vessel on high-resolution MRI, microvascular decompression can be carefully considered as a treatment option for patients with isolated abducens nerve palsy.

Chronic Sixth Nerve Palsy due to Compression by the Anterior Inferior Cerebellar Artery

A 65-year-old healthy woman presented with a 15-year history of binocular horizontal diplopia worse when looking left. She had previously been thoroughly investigated multiple times for a left sixth nerve palsy (6NP) 15 years ago and had three normal magnetic resonance imaging (MRI) scans of the brain/orbits with contrast, normal acetylcholine receptor antibodies, normal thyroid function tests, normal cerebrospinal fluid, and normal nerve conduction studies and single-fibre electromyography. She was treated with prism glasses, which resulted in resolution of her symptoms in primary position.

Magnetic resonance imaging findings of isolated abducent nerve palsy induced by vascular compression of vertebrobasilar dolichoectasia

If the origin of isolated abducent nerve palsy cannot be found on neuroradiological examinations, diabetes mellitus is known as a probable cause; however, some cases show no potential causes of isolated abducent nerve palsy. Here, we report a 74-year-old male who suffered from diplopia due to isolated left abducent nerve palsy. Magnetic resonance angiography and fast imaging employing steady-state acquisition imaging clearly showed a dolichoectasic vertebrobasilar artery compressing the left abducent nerve upward and outward. There were no abnormal lesions in the brain stem, cavernous sinus, or orbital cavity. Laboratory data showed no abnormal findings. We concluded that neurovascular compression of the left abducent nerve might cause isolated left abducent nerve palsy. We observed him without surgical treatment considering his general condition with angina pectoris and old age. His symptom due to the left abducent nerve palsy persisted. From previous reports, conservative treatment could not improve abducent nerve palsy. Microvascular decompression should be considered for abducent nerve palsy due to vascular compression if patients are young, and their general condition is good. We also discuss interesting characteristics with a review of the literature.

Abducent nerve palsy treated by microvascular decompression: a case report and review of the literature

Too few cases of isolated abducent nerve palsy caused by neurovascular compression syndrome have been reported. We here report on a case of abducent nerve palsy caused by neurovascular compression syndrome that was successfully treated by microvascular decompression (MVD). A 46-year-old male presented with a 6-month history of right-sided persistent abducent nerve palsy. High-resolution magnetic resonance imaging revealed a neurovascular contact of the vertebral artery with the right abducent nerve. MVD was performed via a retrosigmoid craniotomy, with remarkable improvement of the palsy. Our report suggests that MVD might be considered as an optional treatment if the symptoms progress or persist.

MRI and neurophysiology in vestibular paroxysmia: contradiction and correlation

BACKGROUND

Vestibular paroxysmia (VP) is defined as neurovascular compression (NVC) syndrome of the eighth cranial nerve (N.VIII). The aim was to assess the sensitivity and specificity of MRI and the significance of audiovestibular testing in the diagnosis of VP.

METHODS

20 VP patients and, for control, 20 subjects with trigeminal neuralgia (TN) were included and underwent MRI (constructive interference in steady-state, time-of-flight MR angiography) for detection of a NVC between N.VIII and vessels. All VP patients received detailed audiovestibular testing.

RESULTS

A NVC of N.VIII could be detected in all VP patients rendering a sensitivity of 100% and a specificity of 65% for the diagnosis of VP by MRI. Distance between brain stem and compressing vessels varied between 0.0 and 10.2 mm. In 15 cases, the compressing vessel was the anterior inferior cerebellar artery (75%, AICA), the posterior inferior cerebellar artery in one (5%, posterior inferior cerebellar artery (PICA)), a vein in two (10%) and the vertebral artery (10%, VA) in another two cases. Audiovestibular testing revealed normal results in five patients (25%), a clear unilateral loss of audiovestibular function in nine patients (45%) and audiovestibular results with coinstantaneous signs of reduced and increased function within the same nerve in six patients (30%). From the 20 TN patients 7, (35%) showed a NVC of the N.VIII (5 AICA, 1 PICA, 1 vein).

CONCLUSIONS

Only the combination of clinical examination, neurophysiological and imaging techniques is capable of (1) defining the affected side of a NVC and to (2) differentiate between a deficit syndrome and increased excitability in VP.

Recurrent isolated abducens nerve paresis associated with persistent trigeminal artery variant

We report a 74-year-old woman who presented with recurrent isolated abducens nerve paresis. Cranial magnetic resonance imaging revealed that the right abducens nerve was sandwiched between the right internal carotid artery and a persistent trigeminal artery (PTA) variant, which might have led to neurovascular compression of the abducens nerve, resulting in abducens nerve damage. Normal variants of PTA, which are cerebellar arteries originating from a precavernous portion of the internal carotid artery, must be carefully observed as such variants can potentially cause a neurovascular compression of the abducens nerve.

Nonaneurysmal cranial nerve compression as cause of neuropathic strabismus: evidence from high-resolution magnetic resonance imaging

PURPOSE

To seek evidence of neurovascular compression of motor cranial nerves (CNs) in otherwise idiopathic neuropathic strabismus using high-resolution magnetic resonance imaging (MRI).

DESIGN

Prospective, observational case series.

METHODS

High-resolution, surface coil orbital MRI was performed in 10 strabismic patients with idiopathic oculomotor (CN III) or abducens (CN VI) palsy. Relationships between CNs and intracranial arteries were demonstrated by 0.8-mm thick, 162-μm resolution, heavily T2-weighted MRI in fast imaging using steady-state acquisition sequences. Images were analyzed digitally to evaluate cross-sectional areas of extraocular muscles.

RESULTS

In one patient with CN III palsy, an ectatic posterior communicating artery markedly flattened and thinned the ipsilateral subarachnoid CN III. Cross-sections of the affected medial, superior, and inferior rectus muscles 10 mm posterior to the globe-optic nerve junction were 17.2 ± 2.5 mm(2), 15.5 ± 1.3 mm(2), and 9.9 ± 0.8 mm(2), significantly smaller than the values of 23.6 ± 1.9 mm(2), 30.4 ± 4.1 mm(2), and 28.8 ± 4.6 mm(2), respectively, of the unaffected side (P < .001). In 2 patients with otherwise unexplained CN VI palsy, ectatic basilar arteries contacted CN VI. Mean cross-sections of affected lateral rectus muscles were 24.0 ± 2.3 mm(2) and 29.8 ± 3.1 mm(2), significantly smaller than the values of 33.5 ± 4.1 mm(2) and 36.9 ± 1.6 mm(2), respectively, in unaffected contralateral eyes (P < .05).

CONCLUSIONS

Nonaneurysmal motor CN compression should be considered as a cause of CN III and CN VI paresis with neurogenic muscle atrophy when MRI demonstrates vascular distortion of the involved CN. Demonstration of a benign vascular cause can terminate continuing diagnostic investigations and can expedite rational management of the strabismus.