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U N I T 1 0
Nervous System
There are as many types of status epilepticus as there
are types of seizures. Tonic–clonic status epilepticus
is a medical emergency and, if not promptly treated,
may lead to respiratory failure and death. The dis-
order occurs most frequently in the young and old.
Morbidity and mortality rates are highest in elderly
persons and persons with acute symptomatic seizures,
such as those related to anoxia or cerebral infarc-
tion.
65
If status epilepticus is caused by neurologic or
systemic disease, the cause needs to be identified and
treated immediately because the seizures probably
will not respond until the underlying cause has been
corrected.
Treatment consists of appropriate life support mea-
sures. Medications are given to control seizure activity.
Intravenously administered diazepam or lorazepam is
considered first-line therapy for the condition. The prog-
nosis is related to the underlying cause as well as the
duration of the seizures themselves.
Neurocognitive Disorders
Neurocognitive disorders involve changes in spectrum
of memory and cognitive functions.
Memory
is the pro-
cess by which information is encoded, stored, and later
retrieved, while cognition is the process by which infor-
mation is reduced, elaborated, transformed, and used.
Cognition
involves the perception of sensory input
and the ability to learn and manipulate new information,
recognize familiar objects and recall past experiences,
solve problems, think abstractly, and make judgments.
Dementia
or nonnormative cognitive decline can be
caused by any disorder that permanently damages large
association areas of the cerebral hemispheres or sub-
cortical areas subserving memory and cognition.
66,67
It
is a common and disabling disorder in the elderly and,
because of the rapidly increasing elderly population, is a
growing public health problem. The disorder is charac-
terized by impairment of short- and long-term memory,
deficits in abstract thinking, impaired judgment and other
higher cortical functions, abnormalities of speech, and
personality changes. These changes eventually become
severe enough that they interfere with day-to-day func-
tioning. Common causes of dementia are Alzheimer
disease, vascular dementia, frontotemporal dementia,
Wernicke-Korsakoff syndrome, and Huntington chorea.
The diagnosis of dementia is based on assessment of
the presenting problem; history about the person that
is provided by an informant (someone who has known
the person, usually a family member); complete physi-
cal and neurologic examination; evaluation of cognitive,
behavioral, and functional status; and laboratory and
imaging studies. Depression is the most common treat-
able illness that may masquerade as dementia, and it
must be excluded when a diagnosis of dementia is con-
sidered. This is important because cognitive function-
ing usually returns to baseline levels after depression is
treated. Screening evaluations for subdural hematoma,
cerebral infarcts, cerebral tumors, and normal-pressure
hydrocephalus are also recommended. These and other
reversible forms of dementia that should be ruled out
can be remembered by the mnemonic DEMENTIA:
D
rugs (drugs with anticholinergic activity),
E
motional
(depression),
M
etabolic (hypothyroidism),
E
yes and ears
(declining vision and hearing),
N
ormal-pressure hydro-
cephalus,
T
umor or other space-occupying lesions,
I
nfection (human immunodeficiency virus infection or
syphilis),
A
nemia (vitamin B
12
or folate deficiency).
67
Alzheimer Disease
Dementia of the Alzheimer type is the most common
type of dementia.
68–70
The disorder affects more than
5.2 million Americans, and is the sixth leading cause of
death.
70
The risk for development of Alzheimer disease
(AD) increases with age, starting at a level of 4% of per-
sons under age 65 years, 13% of persons 65 to 74 years,
44% of persons 75 to 84 years, and 38% of persons age
85 years or older.
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SUMMARY CONCEPTS
■■
Seizures are paroxysmal motor, sensory,
or cognitive manifestations of abnormal
spontaneous electrical discharges from neural
networks in the brain, thought to result directly
or indirectly from changes in excitability of single
neurons or groups of neurons.The site of seizure
generation and the extent to which the abnormal
neural activity is conducted to other areas of the
brain determine the type and manifestations of
the seizure activity.
■■
Focal seizures originate in a small group of
neurons in one hemisphere with secondary
spread of seizure activity to other parts of the
brain. Seizure activity may involve impairment of
consciousness, involuntary motor movements,
somatosensory disturbances, special sensory
sensations, flushing, tachycardia, diaphoresis,
hypotension or hypertension, or pupillary
changes due to stimulation of the autonomic
nervous system.
■■
Generalized seizures show simultaneous
disruption of electrical activity in both
hemispheres from the onset.They include
unconsciousness and varying bilateral degrees
of symmetric motor responses with evidence of
localization to one hemisphere. Absence seizures
are generalized nonconvulsive seizure events
that are expressed mainly by brief periods of
unconsciousness. Tonic–clonic seizures involve
unconsciousness along with both tonic and clonic
muscle contractions.
