One Bite, Two Patients: Disparate Clinical Courses Following Simultaneous Crotalus oreganus abyssus Envenomation.

A number of crotaline species have been associated with neurotoxic envenomation in North America. One clinical sign that can occur is myokymia: fine, involuntary, wave-like muscle movements occurring at regular intervals. We report an unusual scenario in which a single snakebite resulted in simultaneous envenomation of 2 patients. Both developed myokymia, with 1 having respiratory compromise. One patient also developed a hypersensitivity reaction to antivenom. Envenomation by the Grand Canyon rattlesnake, Crotalus oreganus abyssus, can produce significant neurotoxicity and resultant respiratory compromise. Antivenom may be helpful but can produce hypersensitivity reactions.

Superior oblique myokymia.

Superior oblique myokymia (SOM) is a rare condition of unclear etiology. We discuss the history, etiology, clinical features, differential diagnoses, management, and prognosis of SOM. We conducted a meta-analysis of all 116 cases published since SOM was first described in 1906. The age at examination was 17-72 years (mean: 42 years.) There was a right-sided preponderance in 61% of cases (P < 0.02) that was statistically significant in females (63%, P < 0.04) but not in males (59%, P = 0.18). The pathophysiology of SOM may be neurovascular compression and/or ephaptic transmission. Although various pharmacological and surgical approaches to SOM treatment have been proposed, the rarity of the condition has made it impossible to conduct clinical trials evaluating the safety and efficacy of these approaches. Recently, topical beta blockers have managed SOM symptoms in a number of cases, including the first case treated with levobunolol. Systemic medications, strabismus surgery, and neurosurgery have been used to control symptoms, with strabismus surgery carrying a moderate risk of postoperative diplopia in downgaze. Although there is no established treatment for SOM, we encourage clinicians to attempt topical levobunolol therapy before considering systemic therapy or surgery.

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.

Peripheral (limb) myokymic discharges in motor neuron disease.

We present the case of a 28-year-old gentleman who presented with weakness and wasting in the right arm. He complained about painful cramps in his left leg but there were no sensory, visual or swallowing problems. Neurological examination was significant for asymmetric weakness of both upper and lower limbs and deep tendon reflexes were asymmetrically brisk. Initial laboratory investigations, MRI brain and MRI spine were normal. Electromyography revealed active denervation and chronic neurogenic motor unit action potential. Myokymic discharges were noted in the left deltoid muscle.

Agrypnia excitata: current concepts and future prospects in management.

Agrypnia excitata is an extremely rare, life-threatening syndrome characterized by autonomic activation, persistent insomnia, and generalized overactivity. Agrypnia excitata describes a triad of three separate conditions: delirium tremens, Morvan's chorea, and familial fatal insomnia (FFI). Each of the aforementioned three conditions have sleep disturbances as a unifying theme and results in distinct neurophysiological findings. The following is an overview of agrypnia excitata with a particular emphasis placed upon each of the three individual conditions that constitute the syndrome with recommendations on appropriate management.

[Motorocular syndromes due to neurogenic hyperactivity and their treatment]. / Les syndromes oculomoteurs par hyperactivité neurogène et leur traitement.

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.

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.

'Continuous muscle fibre activity' in six dogs with episodic myokymia, stiffness and collapse.

Continuous muscle fibre activity was observed in a crossbred dog, a Yorkshire terrier, a border collie and three Jack Russell terriers. The clinical signs consisted of episodes of generalised myokymia which developed into muscle stiffness and delayed muscle relaxation and generally led to the dogs collapsing into lateral recumbency. These episodes were preceded by intense facial rubbing in three of the dogs, and were associated with severe hyperthermia in five of them. All three Jack Russell terriers showed continuous ataxia. The dogs had above normal activities of aspartate aminotransferase, alanine aminotransferase and creatine kinase, but their cerebrospinal fluid was normal. Myokymic discharges were observed by electromyography in two of the dogs. Two of them were treated with membrane-stabilising agents, with variable results.