The age of onset may be significantly earlier in familial cases, as distinct from sporadic cases. The clinical syndrome is characterized by classical cerebellar symptomology. OPCA presents with a chronic, slowly progressive ataxia that usually begins in the legs, and later also involves the trunk and upper limbs. The patient will exhibit impairment of equilibrium, illustrated by a positive Rhomberg sign, and walk with the typical cerebellar gait characterized by a wide stance and stiff-legged movements. Dysphasia often develops in tandem with dysarthria.
Dysarthria occurs owing to ataxia of the muscles of the larynx.
Articulation is jerky and the syllables are often separate and slurred. Dysarthria and dysphasia are both present from the early stages of the disease, although the signs are usually ignored until there is an obvious problem with chewing and swallowing and articulation becomes affected. Patients may also present with involvement of the muscles of the face and eyes. Nystagmoid jerks are often present, and can be considered simply, an ataxia of the ocular muscles. The facial features will often be marked by facial palsies, and immobile faces.