PARIETAL LOBE EPILEPSIES AND OCCIPITAL LOBE EPILEPSIES

[FHBRADLEY]

PARIETAL LOBE EPILEPSIES AND OCCIPITAL LOBE EPILEPSIES

(I) PARIETAL LOBE EPILEPSIES

Parietal lobe epilepsy syndromes are usually characterized by simple and
secondarily generalized seizures. Most seizures arising in the parietal
lobe remain as simple partial seizures, but complex partial seizures may
arise out of simple partial seizures and occur with spread beyond the
parietal lobe. Seizures arising from the parietal lobe have the following
features: Seizures are predominantly sensory with many characteristics.
Positive phenomena consist of TINGLING AND FEELING OF ELECTRICITY, which
may be confined or may spread in a JACKSONIAN MANNER. There may be a
desire to move a body part or a sensation as if a part were being moved.
Muscle tone may be lost. The parts most frequently involved are those with
the largest cortical representation (e.g., the hand, arm, and face). There
may be tongue sensations of crawling stiffness, or coldness, and facial
sensory phenomena may occur bilaterally. Occasionally an intraabdominal
sensation of sinking, choking, or nausea may occur, particularly in cases
of inferior and lateral parietal lobe involvement. Rarely, there may be
pain which may take the form of a SUPERFICIAL BURNING dysesthesia or a
vague, very SEVERE, PAINFUL SENSATION. Parietal lobe visual phenomena may
occur as HALLUCINATIONS OF A FORMED VARIETY. Metamorphopsia with
distortions, foreshortenings, and elongations may occur, and are more
frequently observed in cases of nondominant hemisphere discharges.
Negative phenomena include NUMBNESS, a feeling that a body part is absent,
and a loss of awareness of a part or a half of the body, known as
asomatognosia. This is particularly the case with nondominant hemisphere
involvement. Severe vertigo or disorientation in space may be indicative
of inferior parietal lobe seizures. Seizures in the dominant parietal lobe
result in a variety of receptive or conductive language disturbances. Some
well-lateralized GENITAL SENSATIONS may occur with paracentral involvement.
Some rotary or postural motor phenomena may occur. Seizures of the
paracentral lobule have a tendency to become secondarily generalized.

(II) Occipital Lobe Epilepsies

Occipital lobe epilepsy syndromes are usually characterized by simple
partial and secondarily generalized seizures. Complex partial seizures may
occur with spread beyond the occipital lobe. The frequent association of
occipital lobe seizures and migraine is complicated and controversial. The
clinical seizure manifestations usually, but not always, include visual
manifestations. Elementary visual seizures are characterized by fleeting
visual manifestations that may be either negative (scotoma, hemianopsia,
amaurosis) or, more commonly, positive (sparks or flashes, phosphenes).
Such sensations appear in the visual field contralateral to the discharge
in the specific visual cortex, but can spread to the entire visual field.
Perceptive illusions, in which the objects appear to be distorted, may
occur. The flowing varieties can be distinguished: a change in size
(macropsia or micropsia) or a change in distance, an inclination of objects
in a given plane of space, and a distortion of objects or a sudden change
of shape (metamorphopsia). Visual hallucinatory seizures are occasionally
characterized by complex visual perceptions (e.g., colorful scenes of
varying complexity). In some cases, the scene is distorted or made
smaller, and in rare instances, the subject sees her/her own image
(heautoscopy). Such illusional and hallucinatory visual seizures involve
epileptic discharge in the temporoparieto-occipital junction. The initial
signs may also include tonic and/or clonic contraversion of the eyes and
head or eyes only (oculoclonic or oculogyric deviation), palpebral jerks,
and forced closure of the eyelids. Sensation of ocular oscillation or of
the whole body may occur. The discharge may spread to the temporal lobe,
producing seizure manifestations of either lateral posterior temporal or
hippo-campoamygdala seizures. When the primary focus is located in the
supracalcarine area, the discharge can spread forward to the suprasylvian
convexity or the mesial surface, mimicking those of parietal or frontal
lobe seizures. Spread to contralateral occipital lobe may be rapid.
Occasionally the seizures tend to become secondarily generalized.