Chapter 027. Aphasia, Memory Loss, and Other Focal Cerebral Disorders (Part 7) doc

Chapter 027. Aphasia, Memory Loss, and
Other Focal Cerebral Disorders
(Part 7)

Gerstmann's Syndrome
The combination of acalculia (impairment of simple arithmetic),
dysgraphia (impaired writing), finger anomia (an inability to name individual
fingers such as the index or thumb), and right-left confusion (an inability to tell
whether a hand, foot, or arm of the patient or examiner is on the right or left side
of the body) is known as Gerstmann's syndrome. In making this diagnosis it is
important to establish that the finger and left-right naming deficits are not part of a
more generalized anomia and that the patient is not otherwise aphasic. When
Gerstmann's syndrome is seen in isolation, it is commonly associated with damage
to the inferior parietal lobule (especially the angular gyrus) in the left hemisphere.
Aprosodia
Variations of melodic stress and intonation influence the meaning and
impact of spoken language. For example, the two statements "He is clever." and
"He is clever?" contain an identical word choice and syntax but convey vastly
different messages because of differences in the intonation and stress with which
the statements are uttered. This aspect of language is known as prosody. Damage
to perisylvian areas in the right hemisphere can interfere with speech prosody and
can lead to syndromes of aprosodia. Damage to right hemisphere regions
corresponding to Wernicke's area can selectively impair decoding of speech
prosody, whereas damage to right hemisphere regions corresponding to Broca's
area yields a greater impairment in the ability to introduce meaning-appropriate
prosody into spoken language. The latter deficit is the most common type of
aprosodia identified in clinical practice—the patient produces grammatically
correct language with accurate word choice but the statements are uttered in a
monotone that interferes with the ability to convey the intended stress and affect.
Patients with this type of aprosodia give the mistaken impression of being
depressed or indifferent.

Subcortical Aphasia
Damage to subcortical components of the language network (e.g., the
striatum and thalamus of the left hemisphere) can also lead to aphasia. The
resulting syndromes contain combinations of deficits in the various aspects of
language but rarely fit the specific patterns described in Table 27-1. In a patient
with a CVA, an anomic aphasia accompanied by dysarthria or a fluent aphasia
with hemiparesis should raise the suspicion of a subcortical lesion site.
Progressive Aphasias
In clinical practice, acquired aphasias are most commonly encountered in
one of two contexts: CVAs and degenerative diseases. Aphasias caused by CVAs
start suddenly and display maximal deficits at the onset. The underlying lesion is
relatively circumscribed and associated with a total loss of neural function at the
lesion site. These are the "classic" aphasias described above where relatively
reproducible relationships between lesion site and aphasia pattern can be
discerned. Aphasias caused by neurodegenerative diseases have an insidious onset
and relentless progression so that the symptomatology changes over time. Since
the neuronal loss within the areas encompassed by the neurodegeneration is partial
and since it tends to include multiple components of the language network,
distinctive clinical patterns and clinico-anatomic correlations are less obvious.
Dementia is a generic term used to designate a neurodegenerative disease
that impairs intellect and behavior to the point where customary daily living
activities become compromised (Chap. 365). Alzheimer's disease is the single
most common cause of dementia. The neuropathology of Alzheimer's disease
causes the earliest and most profound neuronal loss in memory-related parts of the
brain such as the entorhinal cortex and the hippocampus. This is why progressive
forgetfulness for recent events and experiences is the cardinal feature of
Alzheimer's disease. In time, the neuronal pathology in Alzheimer's disease
spreads to the language network and a progressive aphasia, usually of the anomic
type, becomes added to the progressive amnesia. There are other patterns of
dementia, however, where neurodegeneration initially targets the language rather

than memory network of the brain, leading to the emergence of a progressive
aphasia that becomes the most prominent aspect of the clinical picture during the
initial phases of the disease. Primary progressive aphasia (PPA) is the most widely
recognized syndrome with this pattern of selective language impairment.
Clinical Presentation and Diagnosis of PPA
The patient with PPA comes to medical attention because of word-finding
difficulties, abnormal speech patterns, and spelling errors of recent onset. PPA is
diagnosed when other mental faculties such as memory for daily events,
visuospatial skills (assessed by tests of drawing and face recognition), and
comportment (assessed by history obtained from a third party) remain relatively
intact; when language is the major area of dysfunction for the first few years of the
disease; and when structural brain imaging does not reveal a specific lesion, other
than atrophy, to account for the language deficit. Impairments in other cognitive
functions may also emerge, but the language dysfunction remains the most salient
feature and deteriorates most rapidly throughout the illness.