Remission of superior oblique myokymia after microvascular decompression

Recurrent superior oblique myokymia in a patient with retinitis pigmentosa

Superior oblique myokymia is an infrequently encountered condition, presenting with episodes of oscillopsia and/or vertical or oblique nystagmus, accompanied by a fine, monocular, cyclorotational nystagmus. Recent research suggests it is caused by vascular compression of the trunk of the trochlear nerve. The clinical features of a patient reporting three episodes of superior oblique myokymia, each following childbirth, are described. She had previously been diagnosed with retinitis pigmentosa. The possible aetiologies of superior oblique myokymia are described and appropriate assessment and possible referral for further testing detailed.

Therapy of Vestibular Paroxysmia, Superior Oblique Myokymia, and Ocular Neuromyotonia

OPINION STATEMENT

Neurovascular compression syndromes are characterized by recurrent attacks of neurological symptoms and clinical signs depending on the cranial nerve affected. It is assumed that pulsatile compression of the nerve is caused mainly by an artery. The result is segmental demyelination of the transition zone or the central part of the cranial nerve, which is covered by oligodendrocytes, and subsequent ephaptic axonal transmission. Compression of the vestibular nerve can cause attacks of spinning or non-spinning vertigo: vestibular paroxysmia. Compression of the trochlear nerve is characterized by attacks of monocular oscillopsia: superior oblique myokymia. Damage to ocular motor nerves due to local radiation or rarely neurovascular compression can also lead to oscillopsia and double vision precipitated by sustained excentric gaze: ocular neuromyotonia. It is important to note that controlled trials have so far not been performed for any of these three syndromes, mainly because of their low prevalence. Therefore, treatment recommendations are based on single cases or small case series and thus have the lowest level of evidence. The sodium channel blockers carbamazepine (50 to 200 mg tid) or oxcarbazepine (100 to 300 mg tid) are evidently effective in most of the patients who have these three syndromes. However, one should always keep in mind the contraindications, side effects, and interactions with other drugs of carbamazepine ( http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682237.html ) All patients require regular laboratory examinations. Alternatives are other sodium channel blockers such as phenytoin (100 to 300 mg tid), gabapentin (100 to 600 mg tid), or valproic acid (100 to 300 mg tid). Furthermore, there are also few reports on the effects of beta blockers, which may be explained by their reduction of the amplitude of blood pressure. Patients who do not respond to pharmacotherapy require further diagnostics to determine the possibility of other etiologies. Some of these patients benefit from surgical decompression of the affected nerve.

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.

Hemibody pain relieved by microvascular decompression of the contralateral caudal medulla: case report

Microvascular decompression (MVD) of cranial nerves has become an established treatment for trigeminal and (vago)glossopharyngeal neuralgia and for hemifacial spasm. The authors present the case of a 64-year-old man who had a 3.5-year history of severe, drug-resistant hemibody pain with sensory and autonomic disturbance. The ipsilateral trigeminal, cochlear, and glossopharyngeal function also was affected. The contralateral posterior inferior cerebellar artery was seen on magnetic resonance imaging to be indenting the caudal medulla anterolaterally, causing displacement. After MVD of the medulla, there was an immediate and complete resolution of the pain and almost complete resolution of the sensory and autonomic disturbances. The pain later recurred mildly and transiently. The residual symptoms had resolved by 2 years.

Ocular neuromyotonia treated by microvascular decompression: usefulness of preoperative 3D imaging

Ocular neuromyotonia is a rare ocular motility disorder characterized by involuntary contraction of extraocular muscles resulting in paroxysmal diplopia. Although ocular neuromyotonia is reported as a rare complication after radiation therapy, there are a few cases of ocular neuromyotonia in the absence of irradiation. In the reported cases the possibility of vascular compression has been suggested on radiological imaging. The authors report a case of ocular neuromyotonia treated by microvascular decompression of the third cranial nerve, supporting the hypothesis that neurovascular compression may play a role in its pathogenesis. The usefulness of preoperative 3D imaging for microvascular decompression is also discussed.

[Superior oblique myokymia: a report of three cases]

INTRODUCTION

Superior oblique myokymia (SOM/MOS) is an under-recognised and probably under-diagnosed disorder. We describe the clinical signs of this condition among three patients. Next, from review of the literature, we suggest an algorithm for diagnosis and treatment.

OBSERVATION

Retrospective study of three patients aged 40 to 55 presenting with brief, intermittent monocular episodes of oscillopsia.

DISCUSSION

The acute symptomatology of superior oblique myokymia follows a recognizable pattern: it always presents with brief, intermittent monocular vertical oscillopsia and/or vertical diplopia with torsion. The clinical signs are related to a neurogenic hyperexcitability of the superior oblique muscle. Treatment may be medical (carbamazepine, gabapentin, beta-blocker) or surgical. Recent publications report that superior oblique myokymia may result from vascular compression of the trochlear nerve (fourth cranial nerve), which controls the action of the superior oblique muscle, placing this condition in the category of vasculonervous conflicts.

CONCLUSION

Superior oblique myokymia is a relatively poorly known disorder, despite classic pathognomonic symptoms. It is a benign condition, which can nonetheless become incapacitating. It occasionally portends an intracranial pathologic process, which must then be addressed with specific treatment.

Cranial nerve vascular compression syndromes of the trigeminal, facial and vago-glossopharyngeal nerves: comparative anatomical study of the central myelin portion and transitional zone; correlations with incidences of corresponding hyperactive dysfunctional syndromes

OBJECTIVE

The aim of this study was to evaluate the anatomy of the central myelin portion and the central myelin-peripheral myelin transitional zone of the trigeminal, facial, glossopharyngeal and vagus nerves from fresh cadavers. The aim was also to investigate the relationship between the length and volume of the central myelin portion of these nerves with the incidences of the corresponding cranial dysfunctional syndromes caused by their compression to provide some more insights for a better understanding of mechanisms.

METHODS

The trigeminal, facial, glossopharyngeal and vagus nerves from six fresh cadavers were examined. The length of these nerves from the brainstem to the foramen that they exit were measured. Longitudinal sections were stained and photographed to make measurements. The diameters of the nerves where they exit/enter from/to brainstem, the diameters where the transitional zone begins, the distances to the most distal part of transitional zone from brainstem and depths of the transitional zones were measured. Most importantly, the volume of the central myelin portion of the nerves was calculated. Correlation between length and volume of the central myelin portion of these nerves and the incidences of the corresponding hyperactive dysfunctional syndromes as reported in the literature were studied.

RESULTS

The distance of the most distal part of the transitional zone from the brainstem was 4.19  ±  0.81 mm for the trigeminal nerve, 2.86  ±  1.19 mm for the facial nerve, 1.51  ±  0.39 mm for the glossopharyngeal nerve, and 1.63  ±  1.15 mm for the vagus nerve. The volume of central myelin portion was 24.54  ±  9.82 mm(3) in trigeminal nerve; 4.43  ±  2.55 mm(3) in facial nerve; 1.55  ±  1.08 mm(3) in glossopharyngeal nerve; 2.56  ±  1.32 mm(3) in vagus nerve. Correlations (p  < 0.001) have been found between the length or volume of central myelin portions of the trigeminal, facial, glossopharyngeal and vagus nerves and incidences of the corresponding diseases.

CONCLUSION

At present it is rather well-established that primary trigeminal neuralgia, hemifacial spasm and vago-glossopharyngeal neuralgia have as one of the main causes a vascular compression. The strong correlations found between the lengths and volumes of the central myelin portions of the nerves and the incidences of the corresponding diseases is a plea for the role played by this anatomical region in the mechanism of these diseases.

Nystagmus and oscillopsia

The ocular motor system consists of several subsystems, including the vestibular ocular nystagmus saccade system, the pursuit system, the fixation and gaze-holding system and the vergence system. All these subsystems aid the stabilization of the images on the retina during eye and head movements and any kind of disturbance of one of the systems can cause instability of the eyes (e.g. nystagmus) or an inadequate eye movement causing a mismatch between head and eye movement (e.g. bilateral vestibular failure). In both situations, the subjects experience a movement of the world (oscillopsia) which is quite disturbing. New insights into the patho-physiology of some of the ocular motor disorders have helped to establish new treatment options, in particular in downbeat nystagmus, upbeat nystagmus, periodic alternating nystagmus, acquired pendular nystagmus and paroxysmal vestibular episodes/attacks. The discussed patho-physiology of these disorders and the current literature on treatment options are discussed and practical treatment recommendations are given in the paper.

Results of extraocular muscle surgery for superior oblique myokymia

PURPOSE

To report results of extraocular muscle surgery for superior oblique myokymia when medical treatment fails.

METHODS

A retrospective review of 14 consecutive patients undergoing superior oblique tenectomy and inferior oblique myectomy between 1976 and 2008.

RESULTS

The mean age of onset of symptoms was 35.4 +/- 12.6 years (range, 16-59.5), with a mean duration of oscillopsia of 5 +/- 4 years (range, 1.5-17) prior to surgery. Medical treatment was unsuccessful in all 14. Preoperatively, 2 had a small hypertropia that was consistent with an ipsilateral fourth (trochlear) nerve palsy; 12 had no manifest tropia. Postoperatively, all had complete elimination of oscillopsia, and 12 of 14 were free of diplopia in the primary position at 6 meters and 1/3 meter. The only 2 with diplopia in the primary position after surgery were the 2 with a manifest hypertropia preoperatively. Of the remaining 12 patients, 5 had a hypertropia of the affected eye limited to downgaze after surgery (mean of 6.2(Delta) +/- 1.6(Delta)). Of the 5, 3 needed contralateral inferior rectus surgery, and 1 required prism for downgaze. The mean follow-up was 4.1 +/- 2.4 years (range, 0.5-10). At the final visit, none had oscillopsia or uncontrolled diplopia, but 3 (21%) needed prisms.

CONCLUSIONS

Superior oblique tenectomy and inferior oblique myectomy effectively eliminate oscillopsia associated with superior oblique myokymia but result in diplopia in downgaze in approximately 36% of patients, which may cause symptoms in patients who require a bifocal for near work.

[Motorocular syndromes due to neurogenic hyperactivity and their treatment]

In this chapter we describe a variety of rare but clinically identifiable ocular motor syndromes, including ocular neuromyotonia, superior oblique myokymia, ocular motor synkinesis, third nerve palsy with cyclic spasms, and paroxysmal manifestations of multiple sclerosis. These syndromes share many characteristics. They result from neurogenic hyperactivity, causing episodic spasms of one or several extraocular muscles. The pathophysiology is not fully understood, but it usually includes both a focal and partial lesion of one of the ocular motor nerves and a central rearrangement of neuronal activity in the ocular motor nuclei. Treatment with membrane-stabilizing agents, such as carbamazepine, is usually effective to reduce the symptoms. The above-mentioned syndromes result from a number of different diseases. A proportion of apparently idiopathic cases may be related to a neurovascular compression syndrome.

Neurovascular compression of the abducent nerve causing abducent palsy treated by microvascular decompression

✓Isolated abducent palsy is a symptom that can be caused by many different intracranial pathological conditions. In this report the authors describe the case of a patient who suffered isolated abducent palsy resulting from vascular compression of the sixth cranial nerve; surgical treatment consisted of microvascular decompression (MVD).

This 56-year-old man presented with short-lasting episodes of a pulling sensation at the lateral side of his right eye associated with intermittent diplopia, followed by a progressive palsy of the abducent nerve and constant diplopia. Magnetic resonance imaging revealed a neurovascular contact of a dolichoectatic basilar artery with the abducent nerve. The patient underwent surgery consisting of a combined supra- and infratentorial presigmoid approach and subsequent MVD of the abducent nerve. Postoperatively, the abducent nerve palsy resolved within days, and the patient remains free of symptoms with a follow-up time of 4 years.

This is the first report of a neurovascular compression of the abducent nerve treated successfully by MVD.

Oscillopsies : approches physiopathologique et thérapeutique

Oscillopsia is an illusion of an unstable visual world. It is associated with poor visual acuity and is a disabling and stressful symptom reported by numerous patients with neurological disorders. The goal of this paper is to review the physiology of the systems subserving stable vision, the various pathophysiological mechanisms of oscillopsia and the different treatments available. Visual stability is conditioned by two factors. First, images of the seen world projected onto the retina have to be stable, a sine qua non condition for foveal discriminative function. Vestibulo-ocular and optokinetic reflexes act to stabilize the retinal images during head displacements; ocular fixation tends to limit the occurrence of micro ocular movements during gazing; a specific system also acts to maintain the eyes stable during eccentric gaze. Second, although we voluntary move our gaze (body, head and eye displacements), the visual world is normally perceived as stable, a phenomenon known as space constancy. Indeed, complex cognitive processes compensate for the two sensory consequences of gaze displacement, namely an oppositely-directed retinal drift and a change in the relationship between retinal and spatial (or subject-centered) coordinates of the visual scene. In patients, oscillopsia most often results from abnormal eye movements which cause excessive motion of images on the retina, such as nystagmus or saccadic intrusions or from an impaired vestibulo-ocular reflex. Understanding the exact mechanisms of impaired eye stability may lead to the different treatment options that have been documented in recent years. Oscillopsia could also result from an impairment of spatial constancy mechanisms that in normal condition compensate for gaze displacements, but clinical data in this case are scarce. However, we suggest that some visuo-perceptive deficits consecutive to temporo-parietal lesions resemble oscillopsia and could result from a deficit in elaborating spatial constancy.

Jumping Jack Flash

A 38-year-old woman presented with blurred vision and "jumping" of the right eye for 7 months. Magnetic resonance imaging of the head was normal. Intermittent intorsion of the right eye was noted on examination, consistent with superior oblique myokymia. She was initially treated with carbamazepine but stopped after becoming light-headed. The diagnosis and treatment of superior oblique myokymia are discussed.

Nystagmus: an update on treatment in adults

Recent developments in the treatment of nystagmus in adults have changed the traditional approach to such illnesses as benign paroxysmal positional vertigo, vestibular neuritis, Meniere's disease, superior canal dehiscence syndrome, vestibular paroxysmia, superior oblique myokymia, downbeat/upbeat nystagmus and acquired pendular nystagmus, as well as periodic alternating nystagmus. Treatments reported to suppress nystagmus, with tolerable side effects, are now available for some of these syndromes. Due to the absence of large controlled studies, however, treatment recommendations rest only on class C evidence.

Pharmacology of vertigo/nystagmus/oscillopsia

PURPOSE OF REVIEW

To describe recent developments in the pharmacological treatment of vertigo and nystagmus while focusing on vestibular neuritis, Meniere's disease, downbeat nystagmus, periodic alternating nystagmus, acquired pendular nystagmus, and superior oblique myokymia.

RECENT FINDINGS

In the last 2 years several studies have been published on possible pharmacological treatment options for nystagmus and oscillopsia. In the treatment of vestibular neuritis two studies showed that cortisone treatment was effective for restoring labyrinthine function. This benefit seems more likely if treatment is started within the first 2 days of onset. For recurrent vertigo attacks due to Meniere's disease, the titration technique with daily or weekly doses of intratympanic gentamicin until onset of vestibular symptoms, change in vertigo or hearing loss rated best for complete vertigo control. A new pharmacological treatment option for downbeat nystagmus is the administration of potassium channel blockers (e.g. 4-aminopyridine). They are thought to reinforce the inhibitory action of cerebellar Purkinje cells. Several case reports have proven the beneficial effect of baclofen on periodic alternating nystagmus, of gabapentin and memantine on acquired pendular nystagmus, and of carbamazepine and gabapentin on superior oblique myokymia.

SUMMARY

There have been several new developments in the treatment of nystagmus and vertigo over the last 2 years. These include potassium channel blockers for the treatment of downbeat nystagmus, early cortisone treatment to improve recovery of the labyrinth function in vestibular neuritis, and intratympanic gentamicin treatment for Meniere's disease. Other pharmacological treatment options are baclofen for periodic alternating nystagmus, gabapentin and memantine for acquired pendular nystagmus, and carbamazepine for superior oblique myokymia.

Superior Oblique Myokymia Caused by Vascular Compression

A 49-year-old man had left superior oblique myokymia for eight years. Magnetic resonance images with enhanced spoiled gradient recalled acquisition in the steady state (SPGR) and flow imaging using steady acquisition (FIESTA) disclosed a branch of the superior cerebellar artery lying on the root exit zone of the left trochlear nerve. Posterior fossa craniotomy confirmed the imaging findings. A Teflon pad was placed between the compressing artery and the trochlear nerve. The patient's superior oblique myokymia has completely resolved with a one-year follow-up. Only one such case has been previously reported. This is the first report to display the imaging findings.

EFNS task force - therapy of nystagmus and oscillopsia

An overview of possible treatment options for oculomotor disorders that prevent clear vision is given. Downbeat nystagmus, upbeat nystagmus, seesaw nystagmus, periodic alternating nystagmus, acquired pendular nystagmus, and saccadic oscillations such as opsoclonus/ocular flutter are discussed. In addition, superior oblique myokymia and vestibular paroxysmia are reviewed. All treatment recommendations available in the literature are classified as class C only. In general, only some of the patients benefit from the treatment.

Superior oblique myokymia: characteristics and treatment options

Superior oblique myokymia (SOM) is an unusual eye movement disorder characterized by recurring episodes of vertical and torsional microtremor of an eye. Visual symptoms include vertical and torsional diplopia, monocular oscillopsia, and tremerous sensations. The disorder is caused by an abnormal firing of the superior oblique muscle in the affected eye. Three cases of SOM will be presented. One of these patients had improvement of her symptoms from the antidepressant drug mirtazapine (Remeron).

Superior oblique myokymia

Superior oblique myokymia (SOM) is an uncommon, monocular movement disorder involving rapid torsional, low-amplitude contractions of the superior oblique muscle that causes monocular oscillopsia and diplopia. Ocular and neurologic examination in these patients is usually normal, and the clinical course is characterized by exacerbation remissions with good response to medical treatment. In this review, we present recent advances in the pathogenesis of SOM and provide an algorithm for the investigation and management of these patients.

MR anatomy of the proximal cisternal segment of the trochlear nerve: neurovascular relationships and landmarks

PURPOSE

To assess the anatomic features and vascular relationships of the proximal portion of the cisternal segment of the trochlear nerve.

MATERIALS AND METHODS

In 30 subjects (60 nerves) and in one patient with right superior oblique myokymia (SOM), the anatomy of the trochlear nerve was depicted with three-dimensional (3D) Fourier transformation constructive interference in steady state (CISS) magnetic resonance (MR) imaging, whereas the adjacent vessels were detected with 3D time-of-flight (TOF) MR imaging before and after gadopentetate dimeglumine administration. The images were evaluated with respect to the identification of the trochlear nerve, the distance between the point of exit (PE) and the midline, the visualized length, the vascular relationships, and the distance between the PE and the point of neurovascular contact.

RESULTS

3D CISS MR imaging depicted the proximal cisternal segment of the trochlear nerve in the transverse, sagittal, and coronal planes in 57 (95%), 51 (85%), and 48 (80%) of 60 nerves, respectively. The distance from the midline to the PE was 3-9 mm, and the maximum visualized length of the trochlear nerve was 1-14 mm. An arterial-trochlear neurovascular contact was seen at the root exit zone (REZ) in eight (14%) nerves and at a mean distance of 3.4 mm distal to the PE in 29 nerves (51%). The patient with SOM had arterial-trochlear neurovascular contact at the REZ.

CONCLUSION

Use of 3D CISS sequences and 3D TOF sequences with or without gadopentetate dimeglumine enables accurate identification of the proximal cisternal segment of the trochlear nerve and its neurovascular relationships.

Superior oblique myokymia: magnetic resonance imaging support for the neurovascular compression hypothesis

Superior oblique myokymia is a rare movement disorder thought to be caused by vascular compression of the trochlear nerve. Direct display of such neurovascular compression by magnetic resonance imaging has been lacking. The goal of this study was to assess the presence of neurovascular contacts in patients with superior oblique myokymia, using a specific magnetic resonance imaging protocol. A total of 6 patients suffering from right superior oblique myokymia underwent detailed neuro-ophthalmological examination, which showed tonic or phasic eye movement. All patients underwent magnetic resonance imaging, using a magnetic resonance imaging Fourier transform constructive interference in steady-state sequence in combination with magnetic resonance imaging time of flight magnetic resonance arteriography both before and after the administration of Gd-DTPA. With this protocol, the trochlear nerve could be visualized on 11 of 12 sides (92%). Arterial contact was detected at the root exit zone of the symptomatic right trochlear nerve in all 6 patients (100%). No arterial contact was identified at the root exit zone of the asymptomatic left trochlear nerve in any of the 5 left nerves visualized. In conclusion, superior oblique myokymia can result from neurovascular contact at the root exit zone of trochlear nerve, and therefore should be considered among the neurovascular compression syndromes.

Paralytic strabismus

During the past year, many papers described new surgical approaches to correct extraocular muscles paralysis. New advances have been made in the knowledge of ptosis and superior oblique muscle myochymia. Moreover, the author reports sensory problems concerning subjective cyclorotation and binocularity that arise with macular translocation.