The gait disturbance and repeated falling have proved difficult to analyze, as discussed in Chap. 6. Walking becomes increasingly awkward and tentative; the patient has a tendency to totter and fall repeatedly, but has no ataxia of gait or of the limbs and does not manifest a
Romberg sign or orthostatic tremor. Some patients tend to lean and fall backward (retropulsion). One of our patients, a large man, fell repeatedly, wrecking household furniture as he went down, yet careful examination provided no clue as to the basic defect in this “toppling” phenomenon. Along with the oculomotor and balance disorders, there is a gradual stiffening and extension of the neck (in one of our patients it was sharply flexed in a manner consistent with camptocormia) but this is not an invariable finding. The face acquires a staring, “worried” expression with a furrowed brow (a result of the tonic contraction of the procerus muscle), made more striking by the paucity of eye movements. A number of our patients have displayed mild dystonic postures of a hand or foot, especially as the illness advanced but occasionally early on. The limbs may be slightly stiff and there are Babinski signs in a few cases.
The stiffness, slowness of movement, difficulty in turning and sitting down, and hypomimia may suggest a diagnosis of Parkinson disease. However, the facial expression of the PSP patient is more a matter of tonic grimace than of lack of movement, and the lack of tremor, the erect rather than stooped posture, and prominence of oculomotor abnormalities serve to distinguish the two disorders. The signs of pseudobulbar palsy are eventually prominent, and this feature, along with the eye movements, distinguishes the process most conspicuously from other degenerative conditions. The face becomes less expressive (“masked”), speech is slurred in a slowed spastic fashion, quite different from Parkinson disease, the mouth tends to be held open, and swallowing is difficult. Many patients complain of sleep disturbances. The total sleep time and REM sleep are reduced, and spontaneous awakenings during the night are more frequent and longer than in normal individuals of the same age. Complaints of urinary frequency and urgency have also been frequent in advanced cases under our care. Dubois and colleagues proposed an “applause sign” as distinctive to this disease; the patient fails to stop clapping after being asked to do so only 3 times.
The diagnosis often proves difficult to make if the main ocular features are not outstanding. Other features, such as tremor, palilalia, myoclonus, chorea, orofacial dyskinesias, and disturbances of vestibular function, are observed in some cases. Finally the patient becomes anarthric, immobile, and quite helpless. Dementia of some degree is probably present in many cases, but is mild in most. Some patients do become forgetful and appear apathetic and slow in thinking; many others are irritable or at times euphoric.
By MRI one can, in advanced cases, appreciate atrophy of the dorsal mesencephalon (superior colliculi, red nuclei) giving rise to a “mouse ears” configuration (Fig. 38-7A), but these changes may not be evident early in the illness when diagnosis is most difficult. Several measurements of midbrain atrophy have been proposed as aiding diagnosis; for example, there is little overlap between PSP, multiple system atrophy, and Parkinson disease in the ratio of midbrain-to-pons cross-sagittal area, according to Oba and colleagues. The apparent selective atrophy of the dorsal midbrain on mid-sagittal images has been referred to as the “hummingbird sign” (Fig. 38-7B). However, midbrain atrophy must be judged in the context of global brain atrophy (and of the symptoms) in an individual patient. The CSF remains normal. Nonetheless, the diagnosis continues to rest on the clinical features, mainly affecting eye movements.