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U N I T 1 0
Nervous System
that the disease is caused by an insufficiency related to
the mutated gene. Rather, the expansion of the poly-
glutamine region of the HD gene seems to bestow a
toxic gain of function on the protein.
1
Huntington disease produces localized death of
brain cells. The first and most severely affected neu-
rons are those of the basal ganglia that modulate
motor output. These neurons normally function to
dampen motor activity; thus, their degeneration in HD
results in increased motor output, often manifested
as choreiform movements. Although chorea is the
prototypical movement disorder, the full spectrum of
motor impairment in HD includes eye movement dis-
orders, myoclonus, ataxia, dysarthria and dysphagia,
and spasticity. Depression and personality changes are
the most common early psychological manifestations;
memory loss often is accompanied by impulsive behav-
ior, moodiness, antisocial behavior, and a tendency
toward emotional outbursts. Persons with HD uni-
versally go through cognitive decline, mental slowing,
and impaired problem-solving abilities, and eventually
become demented. Cognitive decline also heralds the
juvenile onset of HD.
There is no cure for Huntington disease. The treat-
ment is largely symptomatic. Drugs may be used to treat
the dyskinesias and behavioral disturbances. Genetic
testing can predict whether a person will develop the
disease.
R E V I EW E X E R C I S E S
1.
A 20-year-old man who was an unbelted driver
involved in a motor vehicle accident presents in
coma.
A.
What are the clinical signs of coma?
B.
What areas of the brain are involved in
coma?
C.
Which complications of traumatic head injury
might lead to coma?
D.
What are the key treatment options to manage
elevated intracranial pressure?
2.
A 65-year-old woman presents with a 1-hour
history of right-sided weakness and aphasia. An
immediate CT scan of the brain is negative.
A.
Where in the brain is the pathology?
B.
What are the indications to administer
intravenous tissue plasminogen activator?
C.
What are the possible causes of stroke, and
what diagnostic tests would reveal the
cause?
3.
A child is taken to the emergency department with
lethargy, fever, and a stiff neck on examination.
A.
What findings on initial lumbar puncture
indicate bacterial versus viral meningitis?
B.
In the case of bacterial meningitis, what are the
most likely organisms, and which antibiotics
should be started?
4.
A 60-year-old man develops involuntary shaking of
his right arm that spreads to the face, after which
he collapses with whole-body shaking and loss of
consciousness. After 1 minute, the shaking stops
and he is confused and disoriented.
A.
What type of seizure is suggested by the clinical
manifestations?
B.
Assuming this is his first seizure, what
diagnostic tests should be performed to identify
a cause for the seizure?
C.
If he has a long history of similar recurrent
seizures, what treatments should be instituted?
What treatments should be considered if he has
failed multiple adequate trials of anticonvulsant
medications?
R E F E R E N C E S
1. Frosch MP, Anthony D, DeGirofami U. The central nervous
system. In: Kumar V, Abbas AK, Fausto N, eds.
Robbins and
Cotran Pathologic Basis of Disease
. 8th ed. Philadelphia, PA:
Elsevier Saunders; 2010:1279–1344.
2. Hall JE.
Guyton & Hall Textbook of Medical Physiology
. 12th ed.
Philadelphia, PA: Saunders Elsevier; 2011:742–750.
3. Harukuni I, Bhardwaj A. Mechanisms of brain injury after global
cerebral ischemia.
Neurol Clin.
2006;24:1–21.
SUMMARY CONCEPTS
■■
Cognition refers to all the processes by
which sensory input is transformed, reduced,
elaborated, stored, recovered, and used.
■■
Dementia represents a syndrome of deterioration
in cognitive function severe enough to interfere
with occupational or social performance.The
most common cause of dementia is Alzheimer
disease, an insidious and progressive disorder
that begins with memory impairment and
terminates in an inability to recognize family
or friends and the loss of control over bodily
functions.
■■
Other forms of dementia include vascular
dementia due brain injury resulting
from ischemic or hemorrhagic damage;
frontotemporal dementia with atrophy of
the frontal and temporal lobes; Wernicke-
Korsakoff syndrome most often resulting from
chronic alcoholism; and Huntington disease, a
hereditary disorder characterized by chronic and
progressive chorea, psychological changes, and
dementia.
