Aura continua

Maromi Nei MD (Dr. Nei of Sidney Kimmel Medical College and Thomas Jefferson University received study support fees from Upsher-Smith Laboratories as principal investigator of a drug trial.)
Jerome Engel Jr MD PhD, editor. (Dr. Engel of the David Geffen School of Medicine at the University of California, Los Angeles, has no relevant financial relationships to disclose.)
Originally released May 4, 2001; last updated August 25, 2016; expires August 25, 2019

This article includes discussion of aura continua, simple partial status epilepticus, epileptic hallucination and illusions, prolonged autonomic and psychic phenomena, and subclinical status epilepticus. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Seizures with focal onset may begin with a somatosensory, special sensory, visceral, or experiential aura in up to 83%, depending on the localization of the epileptic discharge and on the accuracy of documentation. Typically, an aura lasts seconds to minutes, is stereotypic, and evolves to other ictal clinical features including loss of awareness. If an aura occurs in isolation, ie, is self-limited in time and without further progression, it is more appropriately called a focal-onset seizure without spread (“simple partial” in the older terminology). Rarely, such symptoms last hours to days (and, according to a report, exceptionally even years) and are then called “aura continua,” ie, represent a form of focal status epilepticus. As with epilepsia partialis continua, the motor counterpart to aura continua, the understanding of the nature of the aura continua in terms of exact pathophysiology awaits clarification. Animal experiments suggest that some neurochemical alterations, including galanin and other inhibitory peptides, might limit neuronal excitability in this peculiar epileptic manifestation.

Historical note and terminology

Galen enshrined the term "aura" into the medical terminology. In Book 3, Chapter 11, he deals with it, saying that "in epilepsy the head is sick, or sometimes the head in association with other organs. . . [epilepsy] can start from the stomachos...” Specifically, Galen coined the term aura (taken from the Greek and originally meaning "breeze") by describing a 13-year-old boy who explained that the condition "originated in the lower leg and then from here climbed upwards . . . as far as to the head; and as soon as it has touched the latter he was no longer able to follow.” Although the patient himself could not tell what exactly rose up, another youth, a better observer, said "that it was like a cold breeze" (Galen 1821).

It is interesting to note that Alexander von Tralleis (6th century) recommended that in patients with such an aura, the therapy should also be directed to the organ affected by the aura. He described a patient in whom he had successfully treated his epilepsy by local application of capsicum to his involved foot (Heintel 1975).

John Hughlings Jackson (1835 to 1911) then described masterly what was later called psychomotor attack by Gibbs and colleagues and Dämmerattacke (twilight attack) by Meyer-Mickeleit (Gibbs et al 1937; Meyer-Mickeleit 1950). Jackson's concept of "a particular variety of epilepsy" (Jackson 1889), the "uncinate fits" also had forerunners. In 1748, Robert Whyatt had described such a condition with gelastic seizures and olfactory aura (Whyatt 1765). Anderson as well as Jackson and Beevor had noted the association of temporal lobe tumors with olfactory hallucinations and dreamy states (Jackson and Beevor 1890; Anderson 1996). However, it was the post mortem finding of a small cystic lesion restricted to the uncinate gyrus in a patient who had suffered from seizures with dreamy states, elaborated automatisms, and amnesia (Jackson and Colman 1898) that led Jackson and Stewart to the concept of "uncinate fits" with "origin of the discharge lesion . . . made up of some cells, not of the uncinate gyrus alone, but of some cells of different parts of a region of which this gyrus is part . .“ (Jackson and Stewart 1899). Modern neurology and epileptology is proud of its achievements, but it is difficult to add much to the early description of Jackson and Stewart:

 

In cases of this group there is at the onset of the paroxysms a crude sensation of smell or one of taste, or there are movements of chewing or smacking the lips, (sometimes there is spitting). In some cases . . . there is warning by what is known as the epigastric sensation, a crude development of a systemic sensation; . . . Different varieties of this group of cases depend . . . on discharge lesions of different parts of what I call the uncinate region . . . it is supposed that especially in this cortical region, not confined to this region, are the physical bases of . . . those systematic sensations, which . . . especially appertain to the digestive system . . . Many of the symptoms of uncinate fits depend, of course, on discharge widespread beyond, some far beyond the uncinate region . . . There is the dreamy state in the paroxysm of many, not of all, cases of the uncinate group of epileptic fits (Jackson and Stewart 1899).

The term "aura" is usually referred to that portion of a seizure experienced before loss of consciousness occurs and for which memory is retained. In the case of simple partial seizure, the aura is the entire seizure; but where consciousness is subsequently lost, the aura is, in fact, the first symptom of a psychomotor or complex partial seizure (Dreifuss 1997).

Scott and Masland first describe somatosensory hallucinations as a "continuous symptom" of an "aura continua” (Scott and Masland 1953). The term "aura continua" can be found in Karbowski as a synonym for continuous psychomotor status (Karbowski 1985; Wieser 2001). Wolf used it as synonym for "status epilepticus of focal sensory seizures" or for hallucinosis (Wolf 1970; Wolf 1980; Wolf 1982).

Wieser describes the problems with the terminology of nonconvulsive status epilepticus, including aura continua (Wieser 2001). In the older terminology, aura continua is a subtype of nonconvulsive status epilepticus and is synonymous with simple partial status epilepticus. The revised 2015 ILAE status epilepticus classification utilizes 4 axes: 1) seizure semiology, 2) etiology, 3) EEG correlates, and 4) age to classify status epilepticus (Trinka et al 2015). In this classification system, aura continua is listed in axis 1 under “Section B.2.b.a,” which includes seizures without prominent motor symptoms and without impairment of consciousness. Under this classification system, there is no specific minimum time duration for seizures to be considered status epilepticus. Instead, seizures are considered to be status epilepticus when there is “failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms which lead to abnormally prolonged seizures (after time point t1). It is a condition that can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures.” For focal status epilepticus with impaired consciousness, t1 (time when a seizure is likely to be prolonged leading to continuous seizure activity) is thought to occur at around 10 minutes. However, a t1 time duration has not been proposed specifically for focal seizures without impaired consciousness, including aura continua.

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