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| Year : 2000 | Volume
: 48
| Issue : 1 | Page : 78-80 |
Episodic ataxia : a case report and review of literature.
Singhvi JP, Prabhakar S, Singh P
Department of Neurology and Radiology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India.
Correspondence Address:
Department of Neurology and Radiology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India.
This report describes the clinical features of a 29 year female presenting with a 3 years history of episodes of cerebellar ataxia, dysarthria and nystagmus lasting 3-5 days, recurring almost every month. Sleep disturbance and buzzing in ears were noted 3-4 days before each episode. No other precipitant factor was present. Family history was negative. She was diagnosed as a case of episodic ataxia type-2 and was successfully treated with acetazolamide, a carbonic anhydrase inhibitor. She was asymptomatic at 2 year followup.
How to cite this article:
Singhvi J P, Prabhakar S, Singh P. Episodic ataxia : a case report and review of literature. Neurol India 2000;48:78-80 |
Intermittent ataxia is well described in several recessively inherited metabolic diseases including Hartnup's disease, pyruvate decarboxylase deficiency, Leigh's disease and the hereditary hyperammonemias.[1] In these conditions, the intermittent ataxia is part of a larger symptom complex, usually including a degree of mental retardation, seizures and often pyramidal dysfunction. In 1946, Parker reported 11 patients with intermittent cerebellar ataxia.[2] Episodic ataxia (EA) is inherited as autosomal dominant trait.[3] The affected members experience discrete episodes of disabling cerebellar disturbance with dysarthria, limb ataxia and dysequilibrium, usually lasting a few hours. At least two distinct forms have been identified, familial EA with interictal myokymia (EA-1) characterised by brief bouts of ataxia lasting minutes and familial EA with interictal nystagmus (EA-2) characterised by longer episodes of ataxia lasting hours to days.[4] The remarkable responsiveness of EA-2 to acetazolamide has been reported.[5] We report the clinical features of a patient with EA-2, in whom no family history could be established.
A 29 year old house wife, mother of two children, presented with 3 year history of episodes of limb and trunkal ataxia, dysarthria, objects appearing as if they were flying, facial grimacing and nystagmus. These episodes were preceded by 3-4 days of sleep disturbance and buzzing sound in ear. Episodes used to subside in 3-5 days, only to recur again. The frequency was once in a month initially, however, later it increased to once in 10 days. No precipitating factor like disturbance in menstrual cycles, pregnancy, exertion, intake of tea, coffee, drugs or dietary changes was present. There was no family history of similar symptoms. In between the attacks, she was noticed to have only horizontal gaze evoked nystagmus. An episode noted 3 days after admission showed limb and trunkal ataxia, dysarthria and nystagmus. No pyramidal or extra pyramidal signs were noted. There was no history of seizures.
Haemogram, urine analysis, liver and renal function, tests, blood sugar, serum calcium, phosporus, lactate and arterial blood gases were within normal limits. Audiometry, evoked potentials, CSF studies and EEG were also normal. MRI of brain showed mild superior cerebellar vermian atrophy [Figure1]. Chromosomal analysis showed no abnormality [Figure2]. Magnetic resonance spectroscopy (MRS) could not be done. A diagnosis of EA-type 2 was made and she was put on acetazolamide 250 mg thrice a day. Follow up upto 2 years showed no recurrence in the first 6 months but when dose of acetazolamide was decreased to 500 mg/day because of burning sensation in hands, two milder episodes were recorded, which lasted for 4-6 hours.
Parker in 1946 gave the first account of periodic ataxia describing 11 patients seen at Mayo Clinic between 1924 and 1943.[2] In seven of these the ataxic episode heralded the onset of multiple sclerosis while in remaining 4 cases there was no obvious underlying neurological dysfunction. Since Parker's original observation, the known causes of periodic ataxia have increased and now include several autosomal recessive and X-linked inborn errors of metabolism.[1],[6],[7] However, all these diseases can be distinguished from the autosomal dominant (AD) episode ataxia on clinical grounds, by the inheritance pattern and obvious difference in their biochemical profile.
There are at least two clinically separate AD disorders characterised by episodic ataxia[4] [Table I]. The first form of EA, called episodic ataxia type 1 (EA-1) is associated with interictal myokymia. Acetazolamide is of benefit in reducing the attack in some kindreds but not others; anticonvulsants may reduce the myokymia and attacks in some patients.[8],[9] The cause of this disorder has been determined to be missense point mutation in the potassium channel gene, KCNA 1, on chromosome 12p.[10] Episodic ataxia type 2 (EA2) is generally associated with interictal nystagmus.[8] Some patients who may or may not have EA develop progressive ataxia and dysarthria.[4] The patient under report belonged to EA-2.
Vighetto et al described MRI findings in familial paroxysmal ataxia.[11] A selective atrophy of the cerebellar vermis, mostly of the anterior part, was demonstrated. Vahedi et al[12] have now established that this disorder is localised to chromosome l9p, similar to familal hemiplegic migraine and cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL).
The basis for its responsiveness to acetazoamide is normalization of elevated pH in the cerebellum.[3] But in sporadic cases of EA, normal pH has been reported in untreated cases. Thus other mechanism of acetazolamide responsiveness may be existing. Other drugs which are effective include anticonvulsants like phenytoin and sodium valproate.
In conclusion, the present communication serves to emphasize the need for a high index of suspicion to diagnose this rare treatable entity. Otherwise the patient will go untreated for years and may land up in psychiatry as a case of somatization disorder, thus increasing the disability and morbidity.
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| 2. | Parker HL: Periodic ataxia. Mayo Clin Proc 1946; 38: 642-645. |
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| 9. | Brunt EP, VanWeerden TW: Familial paroxysmal kinesogenic ataxia and continuous myokymia. Brain 1990; 113: 1361-1382. |
| 10. | Brown DL, Gancher ST, Nutt JG et at: Episodic ataxia/myokymia syndrome is associated with point mutations in the human potassium channel gene, KCNA 1. Nature Genet 1994; 8: 136-140. |
| 11. | Vighetto A, Froment JC, Trillet M et al: Magnetic resonance imaging in familial paroxysmal ataxia. Arch Neurol 1988; 45: 547-549. |
| 12. | Vahedi K, Joutel A, Bogaert PV et al: A gene for hereditary paroxysmal cerebellar ataxia maps to chromosome 19p. Ann Neurol 1995; 37: 289-293 |
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