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Temporal lobe epilepsy
Additional recommended knowledge
Temporal lobe epilepsies are a group of medical disorders in which humans and animals experience recurrent epileptic seizures arising from one or both temporal lobes of the brain. Two main types are internationally recognized.
Because of strong interconnections, seizures beginning in either the medial or lateral areas often involve neighboring areas of the brain. The causes or etiology of different temporal lobe epilepsies vary. MTLE is often associated with generalized tonic-clonic (convulsive) seizures occurring in children under age 8 during fevers (febrile seizures). When MTLE begins in childhood, atrophy of the hippocampus can often be seen on magnetic resonance imaging (MRI) of the brain. When MTLE begins in adulthood, MRIs often reveal no visible abnormalities. Rarely, MTLE can be hereditary or related to brain tumors, spinal meningitis, encephalitis, head injury or blood vessel malformations. MTLE can occur in association with other brain malformations.
Most often, a cause cannot be determined with certainty. LTLE is less common. It can be hereditary, as in Autosomal Dominant Lateral Temporal Lobe Epilepsy (ADLTLE) with auditory or visual features, but can also be associated with tumors, meningitis, encephalitis, trauma, vascular malformations or congenital brain malformations. Again, in many affected persons it is common that no cause can be identified.
The symptoms felt by the patient with TLE and the signs observable by others during seizures depend upon the specific areas of the temporal lobes and neighboring brain areas affected by the seizure. The Classification of Epileptic Seizures published in 1981 by the International League Against Epilepsy (ILAE) recognizes three types of seizures which persons with TLE may experience.
Syndrome of Temporal Lobe Epilepsy (TLE)
The classical syndrome of TLE begins when there is a very early insult to the left or right hippocampus. Newborn babies may develop an infection resulting in a fever. Young babies have an immature thermoregulation system, and the fever causes the baby's core body temperature to increase. The raised body temperature can cause febrile convulsions. These are quite normal in babies, usually lasting only a few minutes, but in a few cases the convulsions can last for an hour. This is a sign that the infant is at a high risk of developing TLE.
There are many oral medications available for the management of epileptic seizures, typically termed anticonvulsants or antiepileptic drugs (AEDs, for short). For temporal lobe epilepsy specifically, the most commonly used AEDs are (historically) phenytoin, carbamazepine, valproate and phenobarbital. Newer drugs, though, like gabapentin, topiramate,Levetiracetam and lamotrigine, promise similar efficacy with fewer side-effects. Nearly all AEDs function by decreasing the excitation of neurons (e.g., by blocking sodium channels or calcium channels) or by enhancing their inhibition (e.g., by potentiating the effects of inhibitory neurotransimitters, like GABA). Unfortunately, many patients with mesial temporal lobe epilepsy (up to one-third) will not experience adequate seizure control with medication. For these patients, resective surgery is the primary alternative. In preparation for these surgeries, patients are monitored by various methods to determine the focus of their seizures (that is, the region of the brain where seizures tend to arise before spreading). This can be done with video-EEG monitoring, intracranial EEG (where electrodes are placed beneath the skull, either within or resting just outside the brain), or SPECT imaging. MRI studies may additionally be used to seek evidence of hippocampal sclerosis. Once the epileptic focus has been determined, it can be excised, which usually involves removing part of the hippocampus and often the amygdala. To avoid removing areas of the brain responsible for speech (so-called "eloquent" areas), the surgical team will conduct a Wada test pre-operatively, wherein sodium amytal is injected in the left or right carotid artery to effectively quiet one half of the brain. If the patient performs poorly on neuropsychological testing after the temporary quieting of a hemisphere, the surgical team will typically do their best to avoid operating on that area.
Temporal Lobe Epilepsy and the Arts
As Eve LaPlante discusses in her book, "Seized," the intense emotions, sensory experience including vibrancy of colors, and particular mental state provoked by temporal lobe abnormalities may have contributed to the creation of significant works of art. A number of well-known writers and artists are known, or in many cases suspected to have had temporal lobe epilepsy, aggravated, in some cases, by alcoholism. They include Charles Dodgson (a.k.a. Lewis Carroll), Edgar Allan Poe, Fyodor Dostoevsky (whose novel The Idiot features an epileptic protagonist, Prince Myshkin), Gustave Flaubert, Philip K. Dick, Sylvia Plath and the contemporary author Thom Jones. Peter O'Leary also discusses this in his book "Gnostic Contagion: Robert Duncan and the Poetry of Illness."
Temporal Lobe Epilepsy, Neurotheology and Paranormal Experience
The first researcher to note and catalog the abnormal experiences associated with TLE was neurologist Norman Geschwind, who noted a constellation of symptoms, including hypergraphia, hyperreligiosity, fainting spells, mutism and pedantism, often collectively ascribed to a condition known as Geschwind syndrome. Vilayanur S. Ramachandran explored the neural basis of the hyperreligiosity seen in TLE using galvanic skin response, which correlates with emotional arousal, to determine whether the hyperreligiosity seen in TLE was due to an overall enhanced emotional response, or if the enhancement was specific to religious stimuli (Ramachandran and Blakeslee, 1998). By presenting subjects with neutral, sexually arousing and religious words while measuring GSR, Ramachandran was able to show that patients with TLE showed enhanced emotional responses to the religious words, diminished responses to the sexually charged words, and normal responses to the neutral words. These results suggest that the medial temporal lobe is specifically involved in generating some of the emotional reactions associated with religious words, images and symbols.
UFO Researcher Albert Budden and cognitive neuroscience researcher Michael Persinger assert that increases in local electromagnetism, triggering the temporal lobe can stimulate TLE and trigger hallucinations of apparent paranormal phenomena, for example ghosts and UFOs. Persinger has even gone as far as to create a "God helmet" to apparently demonstrate how stimulation of the parietal and temporal lobe can evoke altered states of consciousness. Quite possibly, as neurotheologians have speculated, then, individuals with temporal lobe epilepsy, who have a natural aptitude for "religious" states of consciousness (such as euphoria or samadhi) have functioned in human history as religious figures or as shamans. Persinger's theories, however, remain controversial.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Temporal_lobe_epilepsy". A list of authors is available in Wikipedia.|