Hereditary ataxia

We report a sporadic case of spinocerebellar ataxia accompanied by later but severe involvement of the motor neuron system. A 72-year-old man began to show ataxia and dysarthria at age 66 years. Neurological examinations revealed saccadic eye movement, slurred speech, truncal ataxia, pyramidal sign, and urinary disturbance. Neither history of alcoholism nor hereditary factors were found. He developed muscular atrophy of the lower and upper extremities and limb ataxia within three years. Superficial and deep sensations were diminished in both feet four years after onset. Thus, he presented with cerebellar ataxia, bulbar sign, upper and lower motor neuron symptoms, sensory disturbance, and autonomic sign after six years at age 72. The level of serum, creatine phosphokinase (CPK) was increased, and muscle biopsy showed marked neurogenic change. Magnetic resonance imaging (MRI) revealed mild cerebellar and pontine atrophy. Although the combination of spinocerebellar ataxia and motor neuron disease is very rare, the present case suggests the inter-relation of the spinocerebellar and motor neuron systems, and presents peripheral neuropathy as a subtype of multisystem atrophy. [Neurol Res 2000; 22: 567-570]

Keywords: Spinocerebellar ataxia; motor neuron disease, sporadic

INTRODUCTION

Spinocerebellar ataxia is a disease affecting mainly the spinocerebellar systems, but is occasionally associated with degeneration in other systems. Mild muscular atrophy has been reported in some cases of spinocerebellar ataxia type 1 (SCAI )1,2, however, extensive muscular atrophy seen in motor neuron disease is not usually seen. An elevation of creatine phosphokinase (CPK) is also rare in spinocerebellar ataxia. In certain muscle diseases such as polymyositis and Duchenne's progressive muscular dystrophy, the serum CPK may attain a high value, but, in neurogenic muscle diseases it is usually normal or slightly elevated . We report a sporadic case of spinocerebellar ataxia accompanied by severe involvement of the motor neuron system and moderate elevation of CPK.

Case history

A 66-year-old man developed speech disturbance and an unsteady gait. He had no family history of such symptoms. The neurological examination disclosed saccadic eye movement, slurred speech, wide-based and poor tandem walking, poor coordination, hyper-- reaction of both the patellar tendon reflexes, and pollakisuria. Magnetic resonance imaging (MRI) revealed widening of cerebellar sulci and mild pontine atrophy. He was initially diagnosed with olivo-pontocerebellar atrophy (OPCA). The cerebellar symptoms gradually worsened. Three years after onset, bilateral atrophy of the thenar muscle and limb ataxia appeared. The amyotrophy gradually aggravated involving all extremity muscles. Fours years after onset, mild rigidity in the neck, diminution of superficial and deep sensation on both feet, and constipation developed. Furthermore, serum levels of enzymes such as lactic dehydrogenase (LDH), aldolase, and CPK began to increase. On admission to our hospital at age 72, neurological examinations revealed saccadic eye movement, slurred speech, dysphasia, ataxic gait, poor coordination, mild rigidity in neck and marked atrophy of skeletal muscles (Figure IA, B). Deep tendon reflexes of the upper extremities were absent, while both patellar tendon reflex were still hyper-reactive. Plantar reflexes were extensor. Touch, pain, and vibration sensations were diminished on both feet. Position sensation was normal. Constipation and pollakisuria suggested an autonomic system involvement. Laboratory examination revealed an elevation of LDH (582 IU I-1, normal 236 455), CPK (761 IU 1-1, normal 42~258), and myoglobin (255 mg dl-1, normal

DISCUSSION

The patient described here initially presented with truncal ataxia and dysarthria at age 66. At the same time, pyramidal sign and urinary disturbance were also recognized. Over the next three years, limb and distal muscular atrophy became evident. Weakness in the extremities slowly progressed and the man was unable to walk after one year. Four years after onset, mild extrapyramidal sign and sensory disturbance appeared. When we saw this man at age 72, six years after onset, he presented with cerebellar ataxia, bulbar sign, upper and lower motor neuron symptoms, sensory disturbance, and autonomic sign. Thus this case was diagnosed as a case of spinocerebellar ataxia accompanied by subsequent but severe involvement of the motor neuron system.

Mild muscular atrophy has been reported on rare occasions in SCA12 Some cases of SCA2, DRPLA, MDJ, Friedreich ataxia, and GM2 gangliosidosis also present upper or lower motor neuron damage 6, however, extensive muscular atrophy like motor neuron disease is not common in spinocerebellar ataxia. The motor neuron disease KAS presents an elevation of serum CPK level. These diseases were all excluded by DNA analyses in this case. A few cases of Olivo-pontocerebellar atrophy (OPCA) could show mild muscular atrophy with normal CPK in the late stages. However, the symptoms and signs of motor neuron disease were much more prominent in our case than in previously reported OPCA with muscular atrophy-5.

The combination of spinocerebellar ataxia and motor neuron disease is very rare. Only four cases have been reported-10. Clinical features of the present and previous cases show ataxia as the first symptom with subsequent muscular weakness developing within a few years (Table 1). Including the present case, the autonomic system was involved in three of the five reports. In addition, an advanced age at onset, sensory disturbance, and elevation of CPK were characteristic in our patient (Table 1). Serum CPK sometimes elevates by a moderate degree in motor neuron disease Increased CPK level in amyotrophic lateral sclerosis is usually associated with pathological changes in skeletal muscles. In fact, our case presented distal muscular atrophy with marked muscle change (Figure ID).

The etiology of multiple system degenerative diseases is not known. However, we speculate that this unusual combination of system degeneration was not a mere coincidence, but possibly a unique subtype of multisystem atrophy. Recent reports show sporadic ALS presenting with extensive pathological involvement beyond the motor system after surviving for a long period of time on a respirator 12-11. The areas involved consisted of the globus pallidus, subthalamic nucleus, red nucleus, substantia nigra, Clarke's column, intermediolateral nucleus, Onuf's nucleus, middle root zone of the posterior column, and the spinocerebellar tract. Thus, such sporadic ALS cases with extensive involvement beyond the motor system may constitute a distinct subgroup of ALS. Because the initial symptom in our patient was cerebellar ataxia, our case could be differentiated from such sporadic ALS cases. However, the possibility still exists of multiple system degeneration overlapping spinocerebellar and motor neuron systems, and these cases may indicate a common trigger of neurodegeneration in SCA and ALS.

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Yasuhiro Manabe, Yoshihiko Shiro, Koji Takahashi, Kenichi Kashihara and Koji Abe

[epartment of Neurology, Okayama University Medical School, Okayama, Japan

Correspondence and reprint requests to: Yasuhiro Manabe, MD, Department of Neurology, Okayama University Medical School, 2-5-1 Shikata-Cho, Okayama 700-8558, Japan.

[man abe@cc.okayama-u.ac.jpl Accepted for publication January 2000

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