Most neurologists have observed elderly patients in whom the essential abnormality was a progressive asymmetrical extrapyramidal rigidity combined with signs of corticospinal disease. Sometimes a mild postural action tremor beginning unilaterally and suggestive in some respects of Parkinson disease has been added. The parkinsonism is generally unresponsive to l-dopa. These cases have come to be known by the names corticobasal-ganglionic or cortical-basal degeneration and like sounding terms. The relation of such cases to corticostriatospinal degeneration described further on and to frontotemporal lobar degeneration and to progressive supranuclear palsy, is unified by the finding of tau inclusions.
Wenning and colleagues (1994) described a series of such patients in whom the diagnosis was confirmed at postmortem examination. The most common early symptom was an asymmetrical clumsiness of the limbs in half of the patients, with rigidity and, in one-fifth, with tremor; these features are now considered to be the most characteristic early features of the process. As the illness progressed, almost all the patients developed an asymmetric or unilateral akinetic-rigid syndrome, which may be considered the essential motor disorder of this disease, and various forms of gait disorder and dysarthria. Stimulus-induced or spontaneous myoclonus and pyramidal signs, mentioned in other reports and frequent in our cases, were not prominent in their series; limitations of vertical gaze and frontal lobe release signs eventually became apparent in half.
Eventually, although able to exert considerable muscle power, these patients cannot effectively direct their voluntary actions. Attempts to move a limb to accomplish some purposeful act might result in a totally inappropriate movement, always with great enhancement of rigidity in the limb and in other affected parts, or the limb may drift off and assume an odd posture, such as a persistent elevation of the arm without the patient’s awareness—a kind of catalepsy. The disorder of limb function has some of the attributes of a limb-kinetic or an ideomotor apraxia (see Chap. 3), but the hand postures, involuntary movements, and changes in tone are at times more of the type described as “alien hand.” Some patients exhibit anosognosia,
Babinski signs, impaired eyelid or ocular motion (upgaze paresis or abnormal saccadic movements), lingual dyskinesias, frontal release signs, myoclonus, or dysarthria.
Another distinct group has dementia as an early feature, as described by Grimes and colleagues, but mental deterioration is more often late and may not occur in all patients. There are also rare patients who present with behavioral disturbance or nonfluent aphasias as early features, which are difficult to distinguish from subtypes of frontotemporal dementia (Lee and colleagues, 2011). Occasionally, there is some involvement of lower motor neurons with resulting amyotrophy. Several of our patients had myoclonus as an early feature, one displaying it only on one side of the face, the other in an arm. The condition progresses for 5 years or more before some medical complication overtakes the patient.