Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (86 page)

   Drugs that may induce seizures such as crack cocaine, amphetamines, ephedrine, and other sympathomimetics

   Allergic disorders including drug reactions and postvaccinal reactions

   Disorders in amino acid metabolism such as phenylketonuria and maple syrup urine disease

   Disorders in lipid metabolism such as the leukodystrophies and lipidoses

   Glycogen storage diseases

   Infections, meningitis, encephalitis, and postinfectious encephalitis (measles, mumps)

   In the fetus–maternal infection with rubella, measles, and mumps

   Degenerative brain diseases

The diagnosis of seizure requires an excellent history and evaluation of the events leading up to the seizure and the behavior during the seizure and after the seizure. The primary goal is to determine whether the event was a seizure and if so whether it was epileptic or due to a treatable or preventable cause. Electroencephalography (EEG) may be diagnostic in epileptic seizures. It may also determine whether a patient has generalized or partial seizures. Neuroimaging (MRI) should be performed to rule out structural abnormalities in the brain.
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   Laboratory Findings

Laboratory diagnosis is directed at determining an underlying cause of a provoked or nonepileptic seizure. Most important are blood tests for electrolytes, glucose, calcium, magnesium, hematology studies, renal function tests, liver function tests, and toxicology screens. Testing for underlying conditions should be performed as indicated by the history and physical examination. A lumbar puncture is helpful if there is an acute infectious process involving the CNS or the patient has a history of cancer. In other circumstances, the test may be misleading, since a prolonged seizure can cause CSF pleocytosis.
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Carbohydrate metabolism abnormalities may result in seizures with hypoglycemia (glucose <40 mg/dL) or hyperglycemia (glucose >400 mg/dL). Electrolyte imbalance results in neurologic change when sodium is <120 or >145 mEq/L, calcium is <7 mg/dL, or magnesium is low. Hyperosmolality (serum osmolality >300 mOsm/L) may also result in seizure activity.

Laboratory tests that may help to differentiate between seizures and syncope or psychogenic abnormalities include creatinine phosphokinase (CPK), cortisol, white blood cell count, LDH, CO
₂
, and ammonia. CPK may be elevated following generalized seizures but not usually after a partial seizure.
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References

1.  Krumholz A, Wiebe S, Gronseth, G, et al. Practice Parameter: evaluating an apparent unprovoked first seizure in adults (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society.
Neurology.
2007; 69:1996.

2.  Petramfar P, Yaghoobi E, Nemati R, et al. Serum creatine phosphokinase is helpful in distinguishing generalized tonic-clonic seizures from psychogenic nonepileptic seizures and vasovagal syncope.
Epilepsy Behav.
2009;15:330.

DELIRIUM

   Definition

According to the DSM-IV, delirium is defined as having four key features: disturbance of consciousness, change in cognition, development over a short period of time, and an etiology due to medical illness, substance abuse, or intoxication or medication effect. Additional features that may accompany delirium include psychomotor disturbances and emotional disturbances.
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   Clinical Presentation