The primary manifestations are motor or sensory (Table 1.12). The motor features can take the form of jerking, dystonic spasm, posturing or occasionally paralysis,
Table 1.12 Partial seizures of central origin.
Often no loss of consciousness (simple partial seizure) Contralateral clonic jerking (which may or may not march) Contralateral tonic spasm
Posturing, which is often bilateral, and version of head and eyes Speech arrest and involvement of bulbar musculature (producing anarthria or choking, gurgling sounds) Contralateral sensory symptoms Short, frequently recurring attacks which cluster Prolonged seizures with slow progression, and episodes of epilepsia partialis continua Postictal Todd paralysis often with clear consciousness (i.e. simple partial seizures). The jerking can affect any muscle group, usually unilaterally, the exact site depending on the part of the precentral gyrus involved in the seizure, and the jerks may 'march' (the Jacksonian march) from one part of the body to another as the discharge spreads over the motor cortex. The seizure discharge may remain limited to one small segment for long periods of time, and when it does spread it is typically very slow. The clonic jerks consist of brief tetanic contractions of all the muscles that co-operate in a single movement. The seizures spread through the cortex, producing clonic movements according to the sequence of cortical representation. A seizure that begins in the hand usually passes up the arm and down the leg and if it begins in the foot it passes up the leg and down the arm. A seizure beginning in the face is most likely to originate in the mouth because of the correspondingly large area of cortical representation. In seizures arising anywhere in the central region, head and eye version is common. Arrest of speech (anarthria) may occur if the motor area of the muscles of articulation is affected (phon-atory seizure) and is usually associated with spasm or clonic movements of the jaw. After focal seizure activity, there may be localized paralysis in the affected limbs (Todd paralysis), which is usually short-lived.
If the seizure is initiated in or evolves to affect supplementary motor areas, posturing of the arms may develop, classically with adversive head and eye deviation, abduction and external rotation of the contralateral arm and flexion at the elbows. There may also be posturing of the legs, and speech arrest or stereotyped vocalizations. Consciousness is usually maintained unless secondary generalization occurs. The classical posture is named by Penfield the 'fencing posture' (resembling as it does the en garde position), but other postures also occur. The posturing is often bilateral and asymmetric. The fencing posture or fragments of it can also occur in seizures originating in various other frontal and temporal brain regions, presumably due to spread of the seizure discharge to the supplementary motor cortex. In contrast to Jacksonian seizures, supplementary motor area seizures are often very brief, occur frequently and in clusters, sometimes hundreds each day, and are sometimes also precipitated by startle.
Somatosensory or special sensory manifestations (simple hallucinations) occur if the seizure discharge originates in, or spreads to, the post-central region. Typically, these take the form of tingling, numbness, an electrical shock-like feeling, a tickling or crawling feeling, burning, pain or a feeling of heat. These symptoms are usually accompanied by jerking, posturing or spasms as the epileptic discharges usually spread anteriorly. The sensory symptoms may remain localized or march in a Jacksonian manner. Ictal pain is occasionally a prominent symptom and can be severe and poorly localized.
Interictal and ictal scalp EEGs in focal epilepsy in central regions are often normal as the focus may be small and buried within the central gyri.
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