Epilepsy and Seizure Disorders

Generalized Tonic-Clonic (“Grand Mal”) Seizures

This type of seizure can be seen in primary generalized epilepsy syndromes, but it also can occur as a result of diffuse propagation of focal-onset seizures (“secondary generalization”). There is a characteristic progression of features, usually starting with an ictal cry (generated by forced inspiration caused by contraction of the diaphragm combined with contraction of laryngeal muscles); followed by a tonic phase (contraction of muscles in the trunk and limbs); and followed by clonic jerking that generally starts as low-amplitude, high-frequency jerks and progressing to higher-amplitude, lower-frequency jerks. After offset, there is often diffuse decrease in muscle tone, as well as noisy, wet, slow (“stertorous”) breathing. The typical duration of an event is 1 to 2 minutes. Patients are often sleepy or confused for 5 to 30 minutes afterward, sometimes even longer. Patients with rare generalized tonic-clonic seizures often report feeling unwell for hours to days afterward, with muscle soreness, headache, and fatigue. During the tonic phase, patients often develop lateral tongue bite because of tonic contraction of jaw muscles and can develop injuries such as posterior dislocation of the shoulder or compression fractures of thoracic vertebrae. In the absence of an experienced and observant witness, it can be difficult to distinguish this type of seizure from “mimics” such as psychogenic nonepileptic spells (PNESs) or syncope with convulsive features.

Absence (“Petit Mal”) Seizures

These seizures have an abrupt onset; brief duration (typically 10 seconds, and almost always less than a minute); and are characterized by staring, behavioral arrest, amnesia, and sometimes eyelid fluttering or subtle oral automatisms. On EEG, they are associated with a run of 3-Hz generalized spike wave discharges. They are most often seen in neurologically normal children, in disorders such as childhood and juvenile absence epilepsy. Atypical absence seizures usually occur in patients with symptomatic generalized epilepsy (such as in Lennox-Gastaut syndrome), and are longer, with less clear onset and offset.

Myoclonic Seizures

These seizures are seen most often in juvenile myoclonic epilepsy (JME) and can occur either in isolation or preceding a primarily generalized tonic-clonic seizure. They are often brief, lasting only a split second, and are associated with rapid synchronous jerking of proximal muscles, usually without impairment of awareness. In JME, they often occur in the context of sleep deprivation or alcohol use. On EEG, myoclonus is often associated with generalized or bifrontal polyspike-wave discharges.

Tonic Seizures

This type of seizure is seen most often in symptomatic generalized epilepsy syndromes, such as Lennox-Gastaut syndrome. It is associated with sudden, intense, bilateral contraction of proximal (and sometimes distal) muscles, possibly with brief impairment of awareness. They generally last only a few seconds, and there is rapid recovery afterward. On EEG, there is diffuse background attenuation, sometimes with superimposed diffuse, low-voltage, high-frequency (beta) activity. This type of seizure is particularly disabling because it is often associated with a sudden fall if the patient is standing.

Atonic Seizures

These also are most commonly seen in symptomatic generalized epilepsy syndromes. The patient has a brief (usually only a few seconds) loss of tone, resulting in a sudden fall. Patients can often have both tonic and atonic seizures, sometimes with single events that have features of both seizure types. These events are sometimes called “drop attacks” because they result in a sudden loss of posture or tone, which is particularly concerning when the patient is standing or walking. On EEG, there is typically diffuse attenuation, or diffuse low-voltage fast activity.

Focal Seizures Without (“Simple Partial Seizures”) or With Impairment of Awareness (“Complex Partial Seizures”)

The clinical features of focal seizures depend on the region of the brain that is involved. These seizures can have motor manifestations (such as jerking, tonic posturing, loss of tone, widespread hyper motor activity) and can have sensory (including special sensory, such as smell, taste, vision, etc.), autonomic, cognitive, or emotional features, alone or in combination. The unifying feature of this type of seizure is that there is no impairment in the patient’s ability to respond appropriately and remember the incident afterward. This type of seizure typically lasts up to a few minutes in duration, but some patients will feel fatigued for minutes or even hours afterward.

The term aura refers symptoms that occur at the onset of some focal seizures, most commonly sensory symptoms such as smell or taste, cognitive symptoms like déjà vu, or autonomic symptoms like nausea or flushing.

Focal seizures can progress to impairment of awareness, with or without preceding symptoms. The features during impairment of awareness can range from behavioral arrest to automatisms and other motor manifestations.