Peripheral nerve hyperexcitability syndromes / 中华神经科杂志

Peripheral nerve hyperexcitability syndromes (PNHS) encompass a spectrum of a heterogeneous condition with clinical as well as electrophysiological manifestations of peripheral nerve hyperexcitability. The PNHS consist of Isaacs syndrome, Morvan syndrome and Cramp-fasciculation syndrome, which cause widespread symptoms and signs while without evident peripheral nerve disease. Probably the most well-known condition of PNHS is Isaacs syndrome, often called acquired neuromyotonia. Clinical symptoms of PNHS are characterized by muscle twitching, cramps, stiffness, and neuropathic pain. The electrophysiological findings that are very useful in the diagnosis of PNHS are spontaneous myokymic, neuromyotonic, and cramp discharges. An overview of the history, clinical manifestations, pathophysiology, electrophysiological findings and management of PNHS is presented.

Myasthenia in Acquired Neuromyotonia

BACKGROUND: Acquired neuromyotonia (NMT) forms part of the spectrum of acquired peripheral nerve hyperexcitability syndrome, and is thought to be caused by antibodies to voltage-gated potassium channels (VGKC). Exertional weakness is unusual unless autoimmune myasthenia gravis (MG) is superimposed. CASE REPORT: A case of acquired NMT accompanied by exertional weakness without coexistence of seropositive MG is reported herein. CONCLUSIONS: Clinical and electrophysiological observations suggest that the cholinergic overactivity in NMT can compromise the safety factor sufficiently to cause a defect in neuromuscular junction transmission.

Oculomotor Neuromyotonia with Lid Lag

A 52-year-old woman developed episodic diplopia during a period of six months. Between the episodes, depression of the right eye was mildly impaired and lid lag was evident in the right eye on downward gaze. On resuming the primary position after prolonged leftward gaze, she developed a right esotropia and limitation of abduction, elevation, and depression in the right eye. Lid lag may be a sign suggesting oculomotor neuromyotonia in patients with episodic diplopia. The isolated lid lag without lid retraction suggests primary aberrant oculomotor regeneration as a mechanism of this phenomenon.

A Case of Morvan Syndrome

Neuromyotonia, or Isaacs' syndrome, consists of continuous muscle fiber activity caused by hyperexcitability of the peripheral nerves. Rarely, these patients also develop CNS symptoms characterized by confusion, insomnia, hallucinations, and agitation. A rare disease consisting of neuromyotonia, autonomic symptoms, and CNS dysfunction is called Morvan's syndrome. We report a 24-year-old man who presented with insomnia, malaise, anorexia, hyperhidrosis, palpitation and myokymia in both the lower extremities. The pathomechanism of Morvan's syndrome is related to the voltage-gated K+ channel (VGKC) antibodies.

A Case of Idiopathic Ocular Neuromyotonia

Ocular neuromyotonia (ONM) is an episodic involuntary contraction of one or more extraocular muscles, resulting from spontaneous neural discharges of ocular motor nerves. Previous radiation therapy to pituitary or other juxtasellar tumor and vascular compressions are the most common reported causes of ONM. We report one unique case of ONM involving the abducens nerve without any other organic brain lesion and prior radiation therapy.

The Spectrum of Ocular Neutomyotonia / 国际眼科杂志(Guoji Yanke Zazhi)

Objective To probe into the causes, clinical features, diagnosis and treatment of ocular neuromyotonia (ONM). Methods To deeply analyze and discuss the causes, clinical features, diagnosis an treatment of this disease by reporting 4 cases of ONM and refor a pituitary tumor. The spasms occurred in the primary position of gaze and were induced by eccentric gaze. A 72 year-old man had chronic arachnoiditis after myelography with radioactive thorium dioxide many years ago. Spasms of muscles innervated by a third nerve and a sixth nerve were produced by eccentric gaze. Treatment with carbamazepine stopped the ONM in both patients. A 47 year-old man had ONM of a lateral rectus muscle when he looked in eccentric gaze several years after irradiation for a cerebellar medulloblastoma. The spasms occurred when treatment for seizures with carbamazepine was decreased, and resolved with the dosage was increased.A 21 year-old man had recurrence of a congenital hemangioma of the neck, face and brain that caused ONM of a superior oblique muscle many years after it had been partially excised. Downward gaze cau sed the spasms, and they resolved spontaneously. Conclusion ONM begins months to years following treatment for intracranial lesions. Typically, the treatment is radiation for an intracranial tumor, but other eauses of damage to the cranial nerves can produce the syndrome. Spasm of extraocular muscles innervated by the third, fourth or sixth cranial nerves produce strabismus and diplopia, lasting from a few seconds to a few minutes. The spasms are spontaneous or induced by ecceutric gaze that stimulates the affected cranial nerve. Neuroradiologic tests might show abnormalities in or near the cavernous sinus, but usually do not show recurrence of the original tumor. The syndrome rarely resolves spontaneously, but responds well to treatment with carbamazepine.