Partial Epilepsies Differential Diagnoses

Diagnostic Considerations

Understanding the conceptual difference between seizure and epileptic syndrome is important. An epileptic seizure is defined as a transient neurologic dysfunction resulting from an excessive abnormal electrical discharge of cerebral neurons. The clinical manifestations are numerous, including disturbances of consciousness, changes in emotions, changes in sensation, abnormal movements, and changes in visceral functions or behavior.

Epilepsy is a group of disorders characterized by chronic, recurrent, paroxysmal changes in neurologic function caused by abnormalities in electrical activity of the brain. Differentiation of the specific disorders is important for the following reasons:

• It permits determination of prognosis
• It is essential to choosing appropriate drug therapy
• It is essential for surgical treatment

Clinically, seizures may be simple partial or complex partial, with or without secondary generalization. Interictal EEG shows focal spikes or sharp waves, and ictal EEG shows a focal or regional discharge at onset.

Benign epilepsy syndromes are characterized below.

Neonates

In neonates, seizures that occur during sleep manifest as head banging and benign neonatal myoclonus. Seizures during wakefulness may have the following manifestations:

• Jitteriness
• Head banging
• Masturbation
• Benign myoclonus of epilepsy
• Spasmodic torticollis
• Spasms nutans
• Opsoclonus
• Rumination
• Startle disease or hyperexplexia
• Shuddering attacks
• Alternating hemiplegia
• Infantile apnea
• Cyanotic breath-holding spells
• Pallid syncope

Children

In children, seizures that occur during sleep manifest as hypnagogic paroxysmal dystonia, nightmares, night terrors, and sleep walking. Seizures during wakefulness may have the following manifestations:

• Chorea
• Tics
• Paroxysmal choreoathetosis
• Stereotypical movements
• Head nodding
• Headache
• Recurrent abdominal pain
• Rage attacks

Differential diagnostic considerations in these cases include confusional migraine, benign paroxysmal vertigo, stool-withholding activity,^[1] and Munchausen syndrome by proxy.

Late childhood

Seizures during wakefulness may manifest as syncope, narcolepsy and/or cataplexy, basilar migraine, tremor, or panic disorder.

Mesial temporal epilepsy

The most common cause of temporal lobe epilepsy in candidates for epilepsy surgery in adults is hippocampal sclerosis. In children, etiologies are dominated by cortical dysplasias and low-grade neoplasms. Seizures typically are complex partial with automatisms, often preceded by a simple partial phase with sensory symptoms (ie, aura).

Auras commonly observed in temporal lobe epilepsy are epigastric (abdominal) and psychic auras, including déjà-vu or jamais-vu and fear.

Complex partial seizures of temporal lobe origin are semiologically automotor, with fine distal automatisms involving hands and/or fingers and orobuccal movements.

Interictal EEG typically shows temporal sharp waves maximal at anterior temporal or sphenoidal electrodes. Ictal EEG often shows well-defined rhythmic theta seizure patterns.

Diagnosis of mesial temporal lobe epilepsy often is confirmed by high-resolution MRI using dedicated epilepsy protocols. Localization by MRI is a strong predictor of a favorable surgical outcome, especially when concordant with ictal EEG, so much so that performing successful temporal lobectomies without ictal recordings may be possible. The availability and high sensitivity of MRI in this setting has greatly reduced the need for invasive EEG.

Neocortical seizures

Neocortical seizures may be simple partial or complex partial, with symptoms depending on the area of cortex affected. Interictal EEG typically shows sharp waves or spikes outside of the anterior temporal region. Ictal EEG often shows regional or widespread discharges.

In general, localization of the epileptogenic zone by surface EEG (interictal and ictal) is less reliable for neocortical than for mesiotemporal epilepsy. Epileptiform discharges can be absent on surface EEG when the focus is deep, as in supplementary sensorimotor area epilepsy.

Frontal discharges can spread rapidly and mimic primary generalized spike-wave complexes. This is referred to as secondary bilateral synchrony (with interictal epileptiform discharges that appear to be generalized but are in reality secondarily generalized focal discharges). Strict criteria are required to attribute generalized discharges to secondary bilateral synchrony, focal or lateralized epileptiform discharges, or a structural lesion.

Neocortical extratemporal epilepsies may be difficult to localize precisely. Precise localization is important only when considering surgical treatment.

Certain syndromes are well characterized, including frontal, supplementary sensorimotor, parietal, and occipital lobe epilepsies.

Frontal seizures are brief, stereotypical, and often occur in clusters and in sleep. They include behaviors such as bicycling, sexual automatisms, vocalizations, asymmetric tonic extension of proximal extremities, and gestural automatisms. Consciousness may be spared. Owing to the bizarre behaviors, clinically these are often confused as psychogenic nonepileptic attacks.

Parietal seizures often spread to other regions quickly. Somatosensory symptoms such as pain, thermal sensation, or paresthesias contralateral to site of origin are often reported.

Occipital lobe seizures often include vision loss, elementary (flashing white/colored lights) or complex hallucinations, and illusions.^{[2, 3]}

Most adult-onset localization-related epilepsies do not have an identifiable etiology (ie, MRI is most often normal). When a cause is found, it can include various structural lesions (eg, traumatic scars, neoplasms, vascular malformations, strokes, neuronal heterotopias).

Differential Diagnoses

• Absence Seizures
• Benign Childhood Epilepsy
• Epilepsia Partialis Continua
• Epilepsy in Adults with Mental Retardation
• Epilepsy in Children with Mental Retardation
• Epilepsy, Juvenile Myoclonic
• Epileptic and Epileptiform Encephalopathies
• Psychogenic Nonepileptic Seizures