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At a glance

A very rare genetic disorder characterized by predominant neurological syndrome (myoclonus, occasional tonic-chronic seizures, and ataxia) with alteration of cerebellum and globus pallidus. Muscular functions can also be affected. No underlying mitochondrial myopathy.

Synonym

Myoclonus and Ataxia Syndrome.

Genetic inheritance

Autosomal dominant, heterogeneous.

Pathophysiology

Neurological lesions or anomalies are often observed (cerebellar dentate nucleus, degeneration of globus pallidus, elevated cerebrospinal fluid uric acid); muscle biopsy shows the presence of ragged red fibers that probably are caused by mitochondrial abnormalities, which could explain the pathophysiology of this syndrome. Controversy exists about considering Ramsay Hunt Syndrome as a specific entity. Potentially identical to ☞Spinocerebellar Ataxia 14 (SCA-14).

Diagnosis

Association of myoclonus ataxia and occasional seizures. No underlying cause such as mitochondrial myopathy, sialidosis, or ceroid lipofuscinosis can be shown.

Clinical aspects

Neurological signs are isolated. No other association is known. Myoclonus, cerebellar ataxia, intention tremor, and occasional tonic-clonic seizures are the only symptoms.

Precautions before anesthesia

Evaluate the neurological repercussion. Evaluate muscular status especially for the presence of myoclonic tone. Verify ability of patients to use patient-controlled analgesia if necessary.

Anesthetic considerations

The presence of epilepsy must be considered and medication known to stimulate convulsions should be avoided.

Pharmacological implications

The antiepileptic medication must be continued until the morning of surgery. Avoid succinylcholine in presence of muscular abnormalities and potential risk (undocumented) of hyperkalemic response.

Other conditions to be considered

  • Juvenile Paralysis Agitans of Hunt: Autosomal dominant, this syndrome is characterized by mask-like facies, parkinsonism, tremor, bradykinesia, dysarthria, rigidity, gait disturbance, and flexion dystonia of fingers. Progression is slow. Onset in teens or earlier.

  • Dyssynergia Cerebellaris Myoclonica of Hunt (Cerebelloparenchymal Disorder V, Spinodentate Atrophy): Autosomal recessive with ataxia, myoclonic jerks, dentate neuron loss superior, and cerebellar peduncle fiber loss.

  • MERRF Syndrome: Mitochondrial cytopathy evident during adolescence. Progressive myoclonic epilepsy with ragged red fibers in muscle biopsy. Progressive ataxia but little symptomatic myopathy. Occasionally, hypoventilation of central origin.

References

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Bomont  P, Watanabe  M, Gershoni-Barush  R,  et al: Homozygosity mapping of spinocerebellar ataxia with cerebellar atrophy and peripheral neuropathy to 9q33-34, and with hearing impairment and optic atrophy to 6p21-23. Eur J Hum Genet 8(12):986, 2000.  [PubMed: 11175288]
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Hunt  JR: Dyssynergia cerebellaris myoclonica—Primary atrophy of the dentate system: Acontribution to the pathology and symptomatology of the cerebellum. Brain 44:490, 1921.
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Marsden  CD, Obeso  JA: Viewpoints on the Ramsay Hunt syndrome: 1. The Ramsay Hunt syndrome is a useful clinical entity. Move Disord 4:6, 1989.
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Visser  JE, Bloem  BR, van de Warrenburg  BP: ...

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