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  • Updated 05.04.2021
  • Released 05.04.2001
  • Expires For CME 05.04.2024

Aura continua

Introduction

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 stereotyped, 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 (“focal aware” seizures, according to the 2017 ILAE Classification of the Epilepsies). Rarely, such symptoms last hours to days (and rarely 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.

Key points

• Aura continua is a rare phenomenon, difficult to diagnosis, and often occurring with other forms of seizures in the same individual.

• Therapeutic medication trials or specialized testing may be needed to firmly establish the diagnosis.


• Aura continua has varied clinical manifestations, depending on the cortical region of origin, and is often associated with an underlying focal cortical lesion.


• Treatment of aura continua is often difficult and complete seizure freedom is not always possible.

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" (35).

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 (47).

John Hughlings Jackson (1835 to 1911) then described what was later called psychomotor attack by Gibbs and colleagues and Dämmerattacke (twilight attack) by Meyer-Mickeleit (37; 75). Jackson’s concept of "a particular variety of epilepsy" (56), the "uncinate fits," also had forerunners. In 1748, Robert Whyatt had described such a condition with gelastic seizures and olfactory aura (128). Anderson as well as Jackson and Beevor had noted the association of temporal lobe tumors with olfactory hallucinations and dreamy states (54; 04). 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 (55) 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 . .” (56).

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 a focal aware seizure, the aura is the entire seizure; however, where consciousness is subsequently lost, the aura is, in fact, the first symptom of a focal impaired awareness seizure (28).

Scott and Masland first describe somatosensory hallucinations as a "continuous symptom" of an "aura continua” (102). The term "aura continua" can be found in Karbowski as a synonym for continuous psychomotor status (63; 137). Wolf used it as synonym for "status epilepticus of focal sensory seizures" or for hallucinosis (146; Wolf 1980; Wolf 1982).

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 (118). 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.

In the unified EEG terminology and criteria for nonconvulsive status epilepticus published in 2013, aura continua is classified as a form of nonconvulsive status epilepticus without coma or stupor with focal onset and without impairment of consciousness (10).

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