Cerebral palsy can be divided into four broad types:
Each type is characterized by its own pathologic process and causes. Epilepsy is a disorder of cerebral cortex, so the relevant issue in the association of epilepsy with each type of cerebral palsy is the way in which the cortex is affected.
Hemiplegic cerebral palsy typically follows an unremarkable term pregnancy and is noted only as the corticospinal tracts begin to myelinate after the second to third month of life. The most common pathology is a porencephaly or loss of brain volume in the vascular territory of a major cerebral artery, most often the middle cerebral artery. The amount of cortical involvement is determined by the size of the infarct.
The associated epilepsy is typically partial and arises from the border of a porencephalic cyst or from the “scar” of a less severe infarct. Therefore, partial epilepsy can arise from any lobe but usually does not arise from the occipital or inferior temporal cortex, structures perfused by the posterior cerebral artery.
Spastic diplegia is most clearly associated with prematurity. Very low-birth-weight infants (<1500 g birth weight) are at high risk for neurologic disability: 1 in 20 survivors has disabling cerebral palsy.1 The cerebral insult occurs at 26 to 32 weeks of gestation, when the periventricular white matter is especially vulnerable. Periventricular leukomalacia results from ischemia and interrupts the descending corticospinal tracts more from the cortical leg areas than the arm areas. Therefore, many of these children have no cortical lesion, and the rate of epilepsy is relatively low.
If the ischemia has been more severe, then cortical structures may be impaired, but predicting which cortical areas will be most vulnerable is not easy. The epilepsy may be partial, but, if there is global injury, then symptomatic generalized epilepsy may occur.
Interestingly, spastic diplegia sometimes occurs in a term infant. Presumably, this condition is caused by an intrauterine insult at approximately 28 to 32 weeks. Sometimes, a cotwin is known to have died at about this time. It has been suggested that spastic cerebral palsy of unknown etiology in singletons often may be the result of a cotwin death, the so-called vanishing twin syndrome.2
Quadriplegic cerebral palsy has many causes. Sometimes, it is the result of global ischemia, but often it is related to severe global brain malformation. Typically, the cortex is widely involved, and the epilepsies often are of the secondary generalized type.
Dystonic or athetoid cerebral palsy has a variety of causes but usually is believed to result from a brain injury in the last trimester of gestation or the perinatal period. The pathologic process centers on the basal ganglia, and the cortex may be completely spared. Etiologies include kernicterus and hypoxic-ischemic damage. The basal ganglia disorder may be very disabling, especially for tongue and mouth movements, but intelligence may be normal despite severe disability.
Sparing of the cortex means that epilepsy usually is not associated unless the insult has been global and severe. The presence of epilepsy therefore reflects global cortical dysfunction, and symptomatic generalized epilepsies prevail.
Reviewed and revised May 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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