Temporal Lobe Epilepsy

Temporal lobe epilepsy is a form of focal epilepsy, a chronic neurological condition characterized by recurrent seizures. While focal epilepsy accounts for about 50% of all epilepsy cases, the prevalence of temporal lobe epilepsy (TLE) among these cases remains uncertain.

Causes
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.
 * Mesial temporal lobe epilepsy (MTLE) arises in the hippocampus, parahippocampal gyrus and amygdala which are located in the inner aspect of the temporal lobe.
 * Lateral temporal lobe epilepsy (LTLE) arises in the neocortex on the outer surface of the temporal lobe of the brain.

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.

A link between febrile seizures (seizures coinciding with episodes of fever in young children) and subsequent temporal lobe epilepsy has been suggested, but the exact role remains unclear. Some studies have shown abnormalities of the hippocampus on magnetic resonance imaging (MRI) in status epilepticus, which supports the theory that prolonged seizures damage the brain. Interestingly, some cases of MTLE present without the typical changes of mesial temporal sclerosis or other abnormalities on MRI scans. This has been termed paradoxical mesial temporal lobe epilepsy. The epilepsy in these patients tends to occur at a later age, which might suggest that an early event leads to hippocampal damage causing MTLE. Although this theory needs confirmation, some studies have pointed to human herpesvirus 6 (HHV-6) as a possible link between febrile convulsions and later MTLE. Firstly, several studies suggest that HHV-6 infection occurs commonly prior to the occurrence of febrile seizures. However, only a minority of primary HHV-6 infections may be associated with febrile seizures. Secondly, other studies found HHV-6 DNA in brain tissue removed during surgery for MTLE.

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.

Dispersion of granule cell layer in the hippocampal dentate gyrus is a major feature of temporal lobe epilepsy and is linked to the downregulation of reelin, a protein that normally keeps the layer compact by containing the neuronal migration.

Symptoms
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.
 * 1) Simple Partial Seizures (SPS) involve small areas of the temporal lobe and do not affect consciousness. These are seizures which primarily cause sensations. These sensations may be mnestic such as déjà vu (a feeling of familiarity), jamais vu (a feeling of unfamiliarity), a specific single or set of memories, or amnesia. The sensations may be auditory such as a sound or tune, or gustatory such as a taste, or olfactory such as a smell that is not truly present. Sensations can also be visual or involve feelings on the skin or in the internal organs. The latter feelings may seem to move over the body. Dysphoric or euphoric feelings, fear, anger, and other sensations can also occur during SPS. Often, it is hard for persons with SPS of TLE to describe the feeling. SPS are often called "auras," and are sometimes thought to be preludes to more severe seizures.
 * 2) Complex Partial Seizures (CPS) by definition are seizures which impair consciousness to some extent. This is to say that they alter the person's ability to interact with others. They usually begin with an SPS, but then the seizure spreads to a large portion of the temporal lobe and impairs consciousness. Signs may include motionless staring, automatic movements of the hands or mouth, inability to respond to others, unusual speech, or unusual behaviors. Because judgement is impaired, persons experiencing CPS may not legally drive vehicles for periods of time which are set by local governments worldwide.
 * 3) Seizures which begin in the temporal lobe but then spread to the whole brain are known as Secondarily Generalized Tonic-Clonic Seizures (SGTCS). These begin with an SPS or CPS phase initially, but then the arms, trunk and legs stiffen in either a flexed or extended position. After this, coarse jerking of the limbs and trunk occur.

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.

Treatments
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 neurotransmitters, 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 contemporary author Thom Jones. Peter O'Leary has also discussed this in his "Gnostic Contagion: Robert Duncan and the Poetry of Illness". Sadi Ranson-Polizzotti has discussed the significance of Lewis Carroll's epilepsy online and in a forthcoming book on the subject.

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, 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.

Temporal lobe epilepsy and orgasms
In some modes of presentation women can experience orgasms when suffering a temporal lobe epilepsy episode. No cases have so far been reported for men.

Media Depictions

 * Film The Exorcism of Emily Rose, 2005, (directed by Scott Derrickson. The screenplay was written by Scott Derrickson and Paul Harris Boardman.)
 * Film Deceiver, 1997 (directed by Jonas and Josh Pate, starring Tim Roth, Michael Rooker, Chris Penn and Renée Zellweger)
 * Film Happy Accidents, 2001 (directed by Brad Anderson, starring Marisa Tomei and Vincent D'Onofrio)
 * Law and Order: Criminal Intent episode "The Gift," 2003, guest-starring Jane Adams
 * Television show "Veronica Mars," 2004-2007, main character Veronica Mars suspected her ex-boyfriend Duncan Kane of murdering his sister and her best friend, Lilly Kane, after discovering he had been treated for TLE symptoms. (Wrongly described on the show as "Type Four Epilepsy.")
 * Television show "Medium," 2005-, starring Patricia Arquette
 * Television show "Firefly," 2002, film Serenity, 2005, both created by Joss Whedon, feature character River Tam, affected with symptoms of TLE after alteration of amygdala, brain component related to TLE
 * A current story line on the CBS daytime drama, The Young and the Restless, features character Victor Newman being diagnosed with TLE.
 * Television Show "ER," 2007, episode "Crisis of Consciousness", patient predicts engine will fall on his head if he is not moved.
 * Television Show "Daybreak" on ABC, Jared is said to have TLE.
 * Television show "Eli Stone," 2008, title character (Johnny Lee Miller) loosens life and changes priorities after neurological condition prompts auditory/extrasensory hallucinations, premonitions and dawning spiritual enlightenment.
 * Book, "The Terminal Man" by Michael Crichton
 * Book, "The Spiral Staircase" by Karen Armstrong, an autobiography including descriptions of her long undiagnosed Temporal lobe epilepsy.