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At a glance

A very rare and progressive cerebellar dyssynergia with intention tremor first localized to one extremity, convulsions, and myoclonic epileptic jerks. Ragged red fibers are seen on muscle biopsies.

Synonyms

Dentate Cerebellar Ataxia; Dentatorubral Atrophy; Primary Dentatum Atrophy.

History

First described by James Ramsay Hunt, an American neurologist, in 1921.

Genetic inheritance

Autosomal dominant with reduced penetrance.

Pathophysiology

Neurological lesions or anomalies are often observed (cerebellar dentate nucleus, degeneration of globus pallidus, elevated cerebrospinal fluid [CSF] uric acid); muscle biopsy shows presence of ragged red fibers that probably are caused by mitochondrial abnormalities.

Diagnosis

Association of myoclonus ataxia and occasional seizures.

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 (clinical, electroencephalogram [EEG], computed tomography [CT]) and muscular status.

Anesthetic considerations

Patients should be considered epileptic and the use of anesthetic agents inducing seizures should be avoided.

Pharmacological implications

The antiepileptic medication(s) should be continued until the morning of surgery. Because of the presence of muscular abnormalities and risk (undocumented) of hyperkalemic response it is recommended to avoid succinylcholine. Consider interaction between antiepileptic treatment and anesthetic drugs.

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.

References

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Hunt  JR: Dyssynergia cerebellaris myoclonica—Primary atrophy of the dentate system: A contribution 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: PRKCG mutation (SCA-14) causing a Ramsay Hunt phenotype. Mov Disord 22:1024, 2007.  [PubMed: 17343273]

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