Book Review

Imitators of Epilepsy

N Engl J Med 1994; 331:1663December 15, 1994

Article

Imitators of Epilepsy
Edited by Robert S. Fisher. 372 pp. New York, Demos, 1994. $64.95. ISBN: 0-939957-56-6

The variety of ways in which seizures are expressed has made their diagnosis difficult, particularly because the patient cannot describe either the nature or the duration of events. Reliance on electroencephalographic (EEG) patterns can lead to both false positive and false negative diagnoses. Normal variants might be called abnormalities, whereas rare but clearly defined spikes can be missed by an inexperienced reader. The brevity of standard EEG recordings results in a sampling bias that increases false negative results. Recording of the electroencephalogram from the surface of the scalp is insensitive to many deep discharges, particularly from the frontal lobes, which are sparsely covered during routine EEG monitoring. As recently as a decade ago, even experienced epileptologists would fail to recognize seizures originating in the frontal lobes because of the peculiarities of attacks that often looked hysterical. Only a few specialized centers verify abnormalities by recording activity in the depths of the brain. Thus, the diagnosis of epilepsy on the basis of typical signs, symptoms, or routine laboratory tests is not an easy task. Diagnosis is further complicated by the close resemblance of some types of seizure to a variety of other neurologic, psychiatric, and medical disorders.

The 18 chapters of Imitators of Epilepsy thoroughly review the variety of disorders that mimic seizures, as well as describing “seizures that do not look like seizures.” The most common imitators include syncope, cerebrovascular disorders, migraine, sleep and movement disorders, endocrine dysfunction, delirium, hyperventilation, dizziness, and vertigo. Fisher also notes that “patients with functional illness tend to be dysfunctional.” Discussions of these disorders include descriptions of basic physiologic mechanisms and clinical characterizations, as well as aspects of the clinical examination and physiologic and biochemical tests that can be used to differentiate the imitative conditions from seizures. Most of the features discussed raise important medical issues, because the urgency and course of treatment are quite different depending on the diagnosis. In addition to medical mimicry, malingering, episodic dyscontrol, psychogenic seizures, and pseudoseizures are also compared with epileptic seizures.

Several chapters describe the use of prolactin levels in the diagnosis of seizures. However, prolactin levels are highly dependent on how soon a blood sample is obtained after the event, the physiologic severity of the event (localized or generalized in the brain), and the origin of electrical discharge (e.g., frontal or temporal). The fact that prolactin levels often do not rise after seizures originating in the frontal lobes does not help to clarify these difficult-to-diagnose events. The lack of generalizability of such data prevents prolactin levels from being considered a standard tool for diagnosis.

The reader is led through chapters on the intricacies of various simulators of seizures to the concluding chapter on an appropriate, cautious approach to the diagnosis of possible seizures. The book is an excellent overview of the types of question that run through the mind of a diagnostician faced with an event that looks and sounds like a seizure, but that might be an entirely unrelated medical or psychological event. Read it thoroughly to remind yourself to be cautious in making the diagnosis of seizures or epilepsy. Keep the book near the examining room as a handy reference for diagnostic problems.

Joyce A. Cramer, M.D.
Veterans Affairs Medical Center, West Haven, CT 06516