Myokymia in a Patient with Chronic Inflammatory Demyelinating Polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired, immune-mediated neuropathy affecting peripheral nerves and nerve roots. It is characterized by symmetric weakness involving both proximal and distal muscles; it can be relapsing-remitting or progressive in course. The clinical manifestations of CIDP are various and may present with atypical features, like myokymia, tremor, or tremor-like phenomena, which may mislead the clinician in diagnosis.

Morvan's syndrome Presenting with Psychiatric Manifestations - A Case Report and Review of the Literature

The term "la chorιe fibrillare" was used by the French physician Augustine Marie Morvan to describe a syndrome showing hyperactivity features involving the central, autonomic, and peripheral nervous system. The central hyperactivity symptoms are confusion, behavioral problems, hallucinations, myoclonus, and insomnia; the autonomic hyperactivity symptoms are hyperhidrosis and variations in blood pressure; and peripheral hyperexcitability is characterized by painful cramps, myokymia, and neuromyotonia. Here, we present a case that has typical features of Morvan's syndrome and provides a brief description based on available literature.

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.

Neuromuscular tetanic hyperexcitability syndrome associated to a heterozygous Kv1.1 N255D mutation with normal serum magnesium levels

Mutations of the main voltage-gated K channel members Kv1.1 are linked to several clinical conditions, such as periodic ataxia type 1, myokymia and seizure disorders. Due to their role in active magnesium reabsorption through the renal distal convoluted tubule segment, mutations in the KCNA1 gene encoding for Kv1.1 has been associated with hypomagnesemia with myokymia and tetanic crises. Here we describe a case of a young female patient who came to our attention for a history of muscular spasms, tetanic episodes and muscle weakness, initially misdiagnosed for fibromyalgia. After a genetic screening she was found to be carrier of the c.736A > G (p.Asn255Asp) mutation in KCNA1, previously described in a family with autosomal dominant hypomagnesemia with muscular spasms, myokymia and tetanic episodes. However, our patient has always presented normal serum and urinary magnesium values, whereas she was affected by hypocalcemia. Calcium supplementation gave only partial clinical benefit, with an improvement on tetanic episodes yet without a clinical remission of her spasms, whereas magnesium supplementation worsened her muscular symptomatology.

Peripheral Nerve Hyperexcitability Syndromes

PURPOSE OF REVIEW

This article provides a review of the clinical phenotypes and evaluation of peripheral nerve hyperexcitability syndromes. These rare diagnoses include cramp-fasciculation syndrome, Isaacs syndrome, and Morvan syndrome. Recent investigations have led to an understanding of the autoimmune underpinnings of these conditions and their specific associated antibodies. As the presentation of peripheral nerve hyperexcitability syndromes includes muscle stiffness, twitches, and spasms, which are also shared with certain central nervous system and myopathic conditions, the differential diagnosis of peripheral nerve hyperexcitability syndromes is reviewed.

RECENT FINDINGS

Peripheral nerve hyperexcitability syndromes share clinical and electrodiagnostic evidence of motor nerve instability; however, their clinical presentations are varied. Case reviews have helped us understand the spectrum of symptoms associated with the three peripheral nerve hyperexcitability syndromes reviewed here: cramp-fasciculation syndrome, Isaacs syndrome, and Morvan syndrome. More recently, research has focused on understanding the voltage-gated potassium channel complex antibodies as well as neoplasms associated with these conditions.

SUMMARY

The diagnosis of peripheral nerve hyperexcitability syndromes requires a high index of suspicion, support from the physical examination, familiarity with the spectrum of symptoms associated with peripheral nerve hyperexcitability syndromes, and recognition of diagnostic EMG features. Voltage-gated potassium channel complex antibodies are associated with these conditions. Optimum treatment and autoimmune pathogenesis remain areas of active research.

Clinical, laboratory and electrophysiological features of Morvan's fibrillary chorea

Morvan's Fibrillary Chorea (MFC) is a rare autoimmune disorder causally associated with auto-antibodies directed at the voltage-gated potassium channel (VGKC-Abs). It classically presents with sleep disturbances, neuromyotonia and dysautonomia. We aimed to systematically characterise the features of MFC by describing a patient and reviewing published literature. Case notes of 27 patients with MFC (one from our clinic and 26 from the literature) were reviewed and clinical data were extracted and analysed. We found that MFC mainly affects men (96%) and runs a subacute course over months. Neoplasia (56%), VGKC-Abs positivity (79%) and autoimmunity (41%) are frequent associations. Myokymia, insomnia and hyperhidrosis were almost universally described. Other autonomic features were present in 63% with the most common being cardiovascular and bowel disturbances. Clinical, radiological or electroencephalographical features of limbic encephalitis were present in 19% of patients. Outcome was fair with an overall recovery rate of 78%. All patients with malignancies underwent surgery. Immunotherapies including corticosteroids, intravenous immunoglobulins and plasma exchange were instituted in 22 patients and 19 (86%) responded. Of all symptomatic treatments tried, carbamazepine, phenytoin, sodium valproate, levetiracetam and niaprazine were found to be effective. The broad clinical spectrum of VGKC-Abs diseases can make early recognition of MFC difficult. Myokymia, insomnia and hyperhidrosis are invariably present. There may be abnormalities on cerebrospinal fluid testing and VGKC-Abs can occasionally be absent. Early initiation of immunotherapies and malignancy screening are important to prevent adverse outcomes in a condition that generally responds favourably to treatment.

Resolution of superior oblique myokymia with memantine

We describe a novel treatment of superior oblique myokymia. A 40-year-old woman was treated with gabapentin for this disorder with partial success and reported significant side effects including loss of libido and weight gain. After a drug holiday, memantine therapy was initiated resulting in a substantial improvement in her symptoms with far fewer side effects and stability on long-term maintenance therapy.

An interesting case report of Morvan′s syndrome from the Indian subcontinent

The French physician Augustine Marie Morvan first used the term 'la choriotae fibrillare' to describe a syndrome characterized by peripheral nerve hyperexcitability, dysautonomia, insomnia and fluctuating delirium. There are no published reports of the condition from the Indian subcontinent. We report the first such case from the region. Our patient, a 24-year-old male, presented with easy fatigability and stiffness in both the calves for 18 months; continuous twitching of muscles of all four limbs and jaw for two months; hyperhydrosis, palpitations, urinary symptoms, burning dysesthesia in hands, insomnia and abnormal sleep behavior for about a month. Patient had bilateral hyper-reflexia with extensor plantar on the right and equivocal response on the left. Electromyography revealed continuous muscle fiber activity. Thyroid function test, electroencephalography, computerized tomography scan (head) and routine cerebrospinal fluid analysis were normal. The patient showed marked clinical and electrophysiological improvement on prednisolone along with symptomatic therapy over the next two months.

Stiff man-like syndrome and generalized myokymia in spinocerebellar ataxia type 3

We describe the novel association of spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) phenotype combining classical clinical presentation and semeiology mimicking stiff man syndrome (SMS). The studied pedigree comprises seven affected members in three generations. Their clinical picture consisted of cerebellar ataxia, pyramidal signs, facial myokymia, and ophthalmoplegia. The proband was a 39-year-old man in whom such a clinical picture, 5 years after onset at age 29, evolved to severe SMS and widespread myokymia. Electrophysiological study revealed continuous muscle activity in proximal limb muscles. Molecular study demonstrated the MJD gene mutation in all four examined patients with 73 to 76 CAG repeats in the expanded allele. We conclude that an excess of motor unit activity including stiff man-like syndrome and widespread myokymia may be an integral part of the SCA3 clinical spectrum.

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.

Continuous motor unit activity syndromes: a video-polysomnographic study

OBJECTIVE

To ascertain the presence of abnormalities of sleep in patients with continuous motor unit activity with and without symptoms of central nervous system involvement.

METHODS

Five patients with isolated neuromyotonia (Isaacs' syndrome) and 1 patient with Morvan syndrome underwent 24-h videopolysomnographic recording to investigate sleep structure, motor activities and autonomic variables during sleep.

RESULTS

Macro- and microstructural organization of sleep and of the attending autonomic variables were substantially normal in patients with Isaacs' syndrome. On the contrary, sleep structure was severely disrupted with subcontinuous dream enactment and hallucinations in the patient with Morvan syndrome. The pattern of the neuromyotonic discharges, however, was not different between the patients with Isaacs' syndrome compared to Morvan syndrome, the EMG discharges persisting throughout the 24 h of recording and affecting wakefulness and sleep equally.

CONCLUSIONS

Neuromyotonia is compatible with normal organization of sleep. The severe sleep abnormalities observed in Morvan syndrome cannot be simply attributed to the effects of neuromyotonia of peripheral origin.

SIGNIFICANCE

Even though neuromyotonia is common to both Isaacs' and Morvan syndromes, the two conditions differ significantly in regard to CNS involvement with sleep abnormalities and lumping the two conditions together is not justified on clinical and neurophysiological grounds.

Chronic Myokymia Limited to the Eyelid Is a Benign Condition

BACKGROUND

Eyelid myokymia, unlike myokymia of the other facial muscles, is assumed to be a benign, self-limited disorder. However, no systematic follow-up study has been performed on patients with chronic, isolated eyelid myokymia to verify its benign nature.

METHODS

Retrospective single-institution chart review of 15 patients examined between 1983 and 2002 with a diagnosis of isolated eyelid myokymia who have had at least 12 months of follow-up.

RESULTS

In all patients, symptoms began as unilateral, weekly or biweekly, intermittent eyelid spasms, and progressed to daily spasms over several months. The mean duration of symptoms at first examination was 91 months (range 2.5 months to 20 years). In no patient was the myokymia the first manifestation of a neurologic disease, although one patient progressed to ipsilateral hemifacial spasm. Thirteen patients (86.7%) underwent neuroimaging that gave negative results. The myokymia resolved spontaneously in four patients. Of the remaining 11 patients, eight were treated with botulinum toxin injection at regular intervals, with most reporting an improvement in symptoms.

CONCLUSION

Chronic isolated eyelid myokymia is a benign condition. It tends not to progress to other facial movement disorders or to be associated with other neurologic disease. It responds well to treatment with botulinum toxin.

Morvan's syndrome: clinical, laboratory, and in vitro electrophysiological studies

Morvan's syndrome is a rare disorder characterized by neuromyotonia, hyperhidrosis, and central nervous system dysfunction. We report a patient with features of this syndrome, but who initially presented with breathing difficulties. Concentric needle electromyography showed an abundance of myokymic and neuromyotonic discharges. Exercise tests and repetitive nerve stimulation showed a decrement-increment response of compound muscle action potentials. Antibodies against voltage-gated potassium channels were not detected on repeated testing, but the presence of oligoclonal bands in the cerebrospinal fluid (CSF) suggested an autoimmune etiology. At follow-up over 3 years, no cancer was found. Electrophysiological in vitro studies of effects of patient serum and CSF on rat nerves provided no evidence of altered voltage-gated sodium or potassium conductances. We conclude that putative humoral factors do not block ion channels acutely but may cause channel dysfunction with chronic exposure.

X-linked Charcot-Marie-Tooth disease with myokymia: report of a family

The clinical and electrophysiologic profiles of two brothers suffering from Charcot-Marie-Tooth disease are presented. Both had widespread muscle twitching in the legs which showed electrophysiologic features of myokymia. Pedigree analysis suggested an x-linked recessive form of inheritance. This appears to be the first report of an Indian family with x-linked Charcot-Marie-Tooth disease.

Trigeminal myokymia in a young girl

Myokymia results from complex bursts of repetitive discharges of a motor unit typically attributable to a demyelinating condition. We report a 12-year-old girl with unilateral trigeminal myokymia who presented with involuntary jaw movements. Electromyography demonstrated unilateral rhythmic myokymic discharges in the left masseter and temporalis muscles at a rate of 3.5 Hz. Abnormal jaw movements spontaneously resolved over 8 months without treatment or residual deficits. The pathophysiology of myokymic discharges is discussed.

Segmental neurogenic muscle hypertrophy associated with radiation injury

A 48-year-old man presented with painless left trapezius hypertrophy 20 years after radiotherapy for nasopharyngeal carcinoma. EMG sampling showed myokymic discharges, reduced polyphasic motor unit recruitment and no signs of active denervation. The relationship between radiotherapy, brachial plexopathy and neurogenic muscle hypertrophy is discussed.

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.

[Adult GM2 gangliosidosis: improvement of ataxia with GABAergic drugs]

The authors present a case of adult GM2 gangliosidosis, B1 enzymatic type. The main clinical features found were cerebellar ataxia, proximal lower limb weakness and myokymia. The neurological examination, and the biochemical, electrophysiologic and imaging studies are all described. Decreased activity of the enzyme beta-hexosaminidase A in the metabolism of the sulfate substrate 4-MU-NAGS was found in serum. Global cerebellar atrophy was observed in a cranial nuclear magnetic resonance. The electrophysiologic study showed continuous spontaneous activity integrated by myokymia and neuromyotonic discharges in addition to signs of acute and chronic denervation. Disappearance of the myokymia and improvement in the ataxia were attained with the use of the GABAergic drugs gabapentin and tiagabine. The authors try to explain the clinical improvement obtained with the drugs by relating their mechanisms of action to the central nervous system neurotransmitter alterations proposed for this disease.

Morvan's syndrome: peripheral and central nervous system and cardiac involvement with antibodies to voltage-gated potassium channels

Morvan's 'fibrillary chorea' or Morvan's syndrome is characterized by neuromyotonia (NMT), pain, hyperhydrosis, weight loss, severe insomnia and hallucinations. We describe a man aged 76 years with NMT, dysautonomia, cardiac arrhythmia, lack of slow-wave sleep and abnormal rapid eye movement sleep. He had raised serum antibodies to voltage-gated K(+) channels (VGKC), oligoclonal bands in his CSF, markedly increased serum norepinephrine, increased serum cortisol and reduced levels and absent circadian rhythms of prolactin and melatonin. The neurohormonal findings and many of the clinical features were very similar to those in fatal familial insomnia, a hereditary prion disease that is associated with thalamic degenerative changes. Strikingly, however, all symptoms in our MFC patient improved with plasma exchange. The patient died unexpectedly 11 months later. At autopsy, there was a pulmonary adenocarcinoma, but brain pathology showed only a microinfarct in the hippocampus and no thalamic changes. The NMT and some of the autonomic features are likely to be directly related to the VGKC antibodies acting in the periphery. The central symptoms might also be due to the direct effects of VGKC antibodies, or perhaps of other autoantibodies still to be defined, on the limbic system with secondary effects on neurohormone levels. Alternatively, changes in secretion of neurohormones in the periphery might contribute to the central disturbance. The relationship between VGKC antibodies, neurohormonal levels, autonomic, limbic and sleep disorders requires further study.

Vascular compression as a cause of superior oblique myokymia disclosed by thin-slice magnetic resonance imaging

PURPOSE

To describe a case of superior oblique myokymia in which thin-slice magnetic resonance imaging (MRI) appeared to show vascular compression of the trochlear nerve.

METHODS

A 50-year-old woman presented with episodic monocular oscillopsia. Neuro-ophthalmologic examinations showed intermittent intorsional microtremor of her right eye, diagnosed as right superior oblique myokymia. Thin-slice (1.6 mm) MRI, using spoiled gradient recalled acquisition in the steady state, was employed to examine the trochlear nerve in its course through the ambient cistern.

RESULTS

Imaging disclosed a branch of the posterior cerebral artery immediately adjacent to the right trochlear nerve.

CONCLUSION

These magnetic resonance findings suggest that a cause of superior oblique myokymia may be vascular compression of the trunk of the trochlear nerve.

Functional changes and adverse reactions after successful treatment of hereditary myokymia: a case report

Myokymia is a vermiform motion of muscle that can be found in conditions in which there is pathology to the peripheral nerve to that muscle. There are inherited syndromes that can present with muscle cramping and myokymia that have been described, but little information exists on long-term follow-up. In this case study, a 12-year-old girl had an inherited form of myokymia, as determined by clinical examination, electromyographic findings, and family history. The mode of inheritance appeared to be autosomal dominant with reduced penetrance. Carbamazepine was used successfully to treat this disorder. Measurements were made of strength and endurance before and after treatment; significant improvement was seen in endurance with little effect on strength. The patient was able to discontinue carbamazepine without return of symptoms and subsequently was not limited in her activities. Return of symptoms was seen with prednisone treatment for exacerbated asthma. The symptoms resolved with restarting the carbamazepine and weaning of the prednisone. Discussion is presented on the possible mechanism by which anticonvulsant and steroid therapy exert their effects on myokymia.

A case of superior oblique myokymia observed by an image-analysis system

Superior oblique myokymia is a microtremor of the eye that causes monocular torsional oscillopsia. A modified Harada-Ito procedure was used to treat a case of the disease in a 20-year-old woman. The authors used video-image analysis pre- and postoperatively to evaluate the effect of the surgery on abnormal torsional eye movements. This analysis revealed that before surgery, the abnormal torsional movement had a very regular cycle (duration of attack, 8.0 +/- 0.5 s; time interval between attacks, 18.7 +/- 3.2 s; n = 9). After the surgery, amplitude of the abnormal torsional eye movement was reduced, and the oscillopsia had subjectively improved, although the movement cycle remained unchanged. The authors' video-image analysis, which used iris striation, proved to be a useful method for clinical measurement of torsional eye movements.