Sooner or later, gait is characteristically altered in many of the dementias (see Chap. 6). Passive movements of the limbs encounter a fluctuating resistance or paratonia (gegenhalten). Mouthing movements and a number of abnormal reflexes—grasping and sucking (in response to visual as well as tactile stimuli), inability to inhibit blink on tapping the glabella, snout reflex (protrusion of the lips in response to perioral tapping), biting or jaw clamping (bulldog) reflex, corneomandibular reflex (jaw clenching when the cornea is touched), and palmomental reflex (slight retraction of one side of the chin caused by contraction of the mentalis muscle when the palm is stroked)—all occur with increasing frequency in the advanced stages of the dementia. Many of these abnormalities are considered to be motor disinhibitions that appear when the premotor areas of the brain are involved.
In the very later stages, physical deterioration is inexorable. Food intake, which may be increased at the onset of the illness, sometimes to the point of gluttony, is in the end reduced, with resulting emaciation. Finally, these patients remain in bed most of the time, oblivious of their surroundings, and succumb at this stage to pneumonia or some other intercurrent infection. Some patients, should they not die in this way, become virtually decorticate—totally unaware of their environment, unresponsive, mute, incontinent, and adopting a posture of flexion. They lie with their eyes open but do not look about. Food and drink are no longer requested but are swallowed if placed in the patient’s mouth. The term persistent vegetative state is appropriately applied to these patients, although it was originally devised to describe patients in this inert state after cardiac arrest or head injury. Occasionally, diffuse choreoathetotic movements or random myoclonic jerking can be observed, and seizures occur in a few advanced cases. Pain or an uncomfortable posture goes unheeded.
The course of the prototype of dementia, Alzheimer disease, extends for 5 to 10 years or more from the time that the memory defect becomes evident. The clinical course of advanced dementia has been studied by Mitchell and colleagues in nursing homes. Those who acquired pneumonia, a febrile episode or an eating disorder, not surprisingly, had high rates of mortality, approaching half, in the subsequent 6 months.
Naturally, every case does not follow the exact sequence outlined here. Often, a patient is brought to the physician because of an impaired facility with language. In other patients, impairment of memory with relatively intact reasoning power may be the dominant clinical feature in the first months or even years of the disease; or low impulsivity (apathy and abulia) may be the most conspicuous feature, resulting in obscuration of all the more specialized higher cerebral functions. Gait disorder, although usually a late development, may occur early, particularly in patients in whom the dementia is associated with or superimposed on frontal lobe degeneration, Parkinson disease, normal pressure hydrocephalus, cerebellar ataxia, or progressive supranuclear palsy. Insofar as the types of degenerative disease do not affect certain parts of the brain equally, it is not surprising that their symptomatology varies. Moreover, frank psychosis with delusions and hallucinations may be woven into the dementia and are particularly characteristic of certain diseases such as Lewy-body dementia. Chapter 38 discusses these variations and others more fully.