An event characterized only
by changes in autonomic function, behavior, or respiratory rate other
than apnea is referred to as paroxysmal autonomic event, paroxysmal behavioral
event, or paroxysmal respiratory event, respectively.
Paroxysmal behavioral events
are characterized by staring episodes or episodes of hyperalertness.
Paroxysmal autonomic events
are characterized by episodes of flushing and pallor; and sudden changes
in heart rate, blood pressure, or intracranial pressure.
They are very rare.
Respiratory paroxysmal events
are characterized by bouts of rapid or slow breathing.
The term seizure refers to
any clinical paroxysmal event believed or proven to be associated with:
(1) scalp-recorded or
cortically-recorded electroencephalographic seizures, (2) a focal cerebral
hemispheric increased isotope uptake by single photon emission computed
tomography, or (3) rSO2 fluctuations by
scalp recorded near infrared spectroscopy.
The term seizure should not
be used for a clinical paroxysmal event believed or proven not to be associated
with scalp-recorded electroencephalographic seizures, cortically-recorded
cerebral or cerebellar electroencephalographic seizures, focal hemispheric
increased isotope uptake by single photon emission computed tomography,
or rSO2 fluctuations by scalp recorded near infrared spectroscopy.
The term electroencephalographic
seizure refers to any scalp- or cortically-recorded electroencephalographic
pattern considered to result from pathological, massive, and repetitive
neuronal depolarization. An electroencephalographic pattern recorded from
scalp electrodes is interpreted as an electroencephalographic seizure
if it is rhythmic; has an electrical field; has a precise onset, body,
and offset; and is not considered to be physiologic or
artifactual in nature (click on clip).
originate from the cerebral cortex but some originate from the cerebellum.
The term cerebellar seizures refers to any clinical paroxysmal event believed
or proven to be due to pathological, massive, and repetitive cortical
cerebellar neuronal depolarization. Cerebellar seizures are characterized
by hemifacial contraction (click on clip),
head and eye deviation, nystagmus and autonomic dysfunction; consciousness
is usually not affected.
They occur with cerebellar tumors.
Facial spasms due to cerebellar
seizures may be very subtle. Ipsilateral arm contraction is often present
(click on clip).
The patient in the last
two clips had tuberous sclerosis and a large cerebellar subependymal
giant cell astrocytomas (Figure 2.1).
Figure 2.1.— [A]
Sagittal MRI of the brain demonstrating a large posterior fossa tumor
(contrast) and dilatation of the third ventricle. [B] Hematoxylin-eosin
stain of tumor tissue demonstrating a solid proliferation of large balloon
cells with abundant glassy to finely granular or foamy eosinophilic
cytoplasm with frequent eccentric uniformly regular nuclei with bland
chromatin and a distinct nucleoli. The histology was consistent with
a subependymal giant cell astrocytomas.