Ataxia (from the Greek “without order”) denotes incoordination and imbalance, involving limbs, stance, and gait, as well as speech and ocular disturbances. In practice, the term is used when these symptoms arise from neurologic dysfunction involving the cerebellum and its connecting pathways. However, ataxia can also result from malfunction of sensory input from proprioceptive sensory pathways or the vestibular system into the cerebellum. Ataxia often results in significant loss of independence, and injuries from falls as well as other complications lead to considerable morbidity.
APPROACH TO THE ATAXIC PATIENT
Once ataxic features of coordination or gait are recognized, cerebellar ataxia needs to be distinguished from so-called “sensory ataxia” resulting from proprioceptive abnormalities, and from labyrinthine ataxia seen with vestibular disorders. With proprioceptive ataxia, incoordination often increases dramatically when the patient’s eyes are closed. Oculomotor symptoms such as nystagmus point away from sensory ataxia. Patients with labyrinthine ataxia also have impaired gait and balance, but speech is not affected and limb movements are coordinated. Myelopathy, basal ganglia disease, or bihemispheric disease can also cause incoordination and gait dysfunction. It is therefore important in assessing ataxia to make sure that the clumsiness observed is independent of isometric strength, muscle tone, reflex abnormalities, and problems with spatial planning. In practice, however, the clinical picture may be complicated by coexistence of these abnormalities with cerebellar disease.
Because ataxia may result from acquired disorders or be genetically determined (Table 16–1), a careful family history is necessary. The time course of disease, age of onset, additional symptoms such as spasticity or cognitive dysfunction, and evidence of systemic disease help refine diagnostic possibilities.
Table 16−1.Causes of ataxia: categories of diseases affecting the cerebellum and time course of disease. ||Download (.pdf) Table 16−1. Causes of ataxia: categories of diseases affecting the cerebellum and time course of disease.
|Category ||Disease ||Time Coursea |
|Acute ||Subacute ||Chronic |
|Developmental ||Arnold-Chiari malformation, Dandy-Walker malformation, cerebellar hypoplasia ||− ||− ||+ |
|Hereditary ||Autosomal-dominant spinocerebellar ataxias (see Tables 16–6 and 16–7) ||− ||− ||+ |
|Autosomal-recessive spinocerebellar ataxias—Friedreich ataxia, others (see Table 16–9) ||− ||− ||+ |
|Fragile X-associated tremor and ataxia syndrome ||− ||− ||+ |
|Episodic ataxias (see Table 16–8) ||+ ||− ||(+) |
|Mitochondrial disorders (see Table 16–10) ||+ ||+ ||+ |
|Leukodystrophies, storage disorders ||− ||− ||+ |
|Urea cycle disorders ||+ ||+ ||+ |
|Vascular ||Ischemic cerebellar stroke (see Table 16–4), ataxic hemiparesis, lacunar stroke syndrome ||+ ||− ||− |
|Cerebellar hemorrhage ||+ ||− ||− |
|Arteriovenous malformations ||+ ||+ ||+ |
|Cavernous malformations ||+ ||− ||− |
|Toxin-associated ||Alcohol ||+ ||+ ||+ |
|Metals (lead, thallium, mercury) ||+ ||+ ||+ |
|Solvents ||+ ||− ||+ |
|Medication-associated ||Anticonvulsants (phenytoin, carbamazepine), amiodarone, cytotoxic drugs (methotrexate, cisplatin) ||+ ||+ ||+ |
|Neoplastic ||Metastatic tumors (lung, breast, melanoma, renal, seminoma, teratoma) ||− ||+ ||+ |
|Medulloblastoma, glioma, oligodendroglioma, astrocytoma, meningioma, ependymomas, cerebellopontine tumors ||− ||+ ||+ |
|Cerebellar hemangioblastoma ...|