Confused about seizures

David dhe at er6.rutgers.edu
Sun Jan 15 22:07:45 EST 1995


mlm2s at galen.med.Virginia.EDU (Mallory Leslie McClure) writes:

>I am totally confused about the different types of seizures.
[...]

Warning:  I'm not an expert.  I just happened to get here first.

I got this information from a chapter by Vernon M. Neppe and Gary
J. Tucker in _The American Psychiatric Press Textbook of
Neuropsychiatry_ (second edition, 1992), and from Jeffrey L.
Cummings' _Clinical Neuropsychiatry_ (1985).

First, here's a 1981 classification from the International League
Against Epilepsy Commission:
============================================================
1. generalized seizures (convulsive or nonconvulsive):          
     A. a) absence (formerly "petit mal")
        b) atypical
     B. tonic-clonic (formerly "grand mal")
     C. myoclonic
     D. clonic
     E. tonic
     F. atonic
     G. combinations

2. partial (or "focal" or "local") seizures:
     A. simple: motor, somatosensory, autonomic, or psychic
     B. complex:
          a) impaired consciousness at outset
          b) simple partial followed by impaired consciousness 
     C. partial seizures evolving to generalized seizures
============================================================

Generalized seizures have no localizable cortical focus; as soon as
they arise, they spread throughout the neocortex of both cerebral
hemispheres, presumably via subcortical structures.  There are no
preceding motor or perceptual experiences, except maybe brief stomach
pain.  There is often an outcry, and almost always a total loss of
consciousness.  The seizure usually lasts 2 to 5 minutes.

The most common type of generalized seizure is tonic-clonic (or "grand
mal"): short tonic movements of muscles (extension or flexion, with no
shaking, for 10 to 30 seconds), followed 15 to 60 seconds of clonic
movements (rhythmic shaking of muscle groups).

Another type of generalized seizure is an absence (or "petit mal")
seizure, in which there is loss of consciousness for a few seconds,
with eye or muscle flutterings at a rate of 3 per second, without loss
of muscle tone.

In a partial seizure, there is a focus (one localizable part of the
brain where epileptic firing begins).  The seizure evokes the
experience that would be produced by direct electrical stimulation of
the focus.  Often there are preceding motor or perceptual experiences.

When partial seizures evoke no change in consciousness, they are said
to be simple.  When partial seizures do evoke a change in
consciousness (such as sensory distortions, hallucinations, deja vu,
sudden fear or depression, or depersonalization), they are said to be
complex.  Complex partial seizures are sometimes further subdivided
into "temporal" and "extratemporal."

When people use the term "temporal-lobe epilepsy," they're usually
referring to something like "complex-partial-seizure disorder"--but
the correlation is imperfect.  Temporal-lobe seizures aren't always
complex partial seizures, and complex partial seizures don't always
have their foci in the temporal lobe.

Reminder: I'm not an expert.  There are probably places where this
post should be corrected.

--David



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