Medically refractory epilepsy in autism concludes that treatment resistant epilepsy in autism affected individuals has less favorable result outcome when intervened upon with nerve stimulation or surgery.
Epilepsy rates within the autism population are reported to be at approximately 20% to 35%. About 25% begin to experience seizure during puberty. Hormonal changes during puberty probably contribute to the manifestation of seizure activity in many cases.
A subset within the autism population experience sub-clinical seizures which cannot be easily detected via simple observation - and are detected through EEG.
Some possible signs of sub-clinical activity include the following: exhibiting behavior problems, such as aggression, self-injury, and severe tantrums; making little or no academic gains after doing well during childhood and pre-teen years; and/or losing some behavioral and/or cognitive gains. (link)
There are seizure disorders not detectable via EEG; One such type of seizure disorder is Paroxysmal Nonepileptic Disorder (PNED). Paroxysmal Nonepileptic Disorders of Childhood gives attention to the a 25% rate of children with diagnoses of epileptic seizure who might instead have paroxysmal involvement.
It is important to identify when, and if, PNED is present so that children are not inappropriately placed on medications that usually only provide benefit for seizure detected via EEG. PNED reveals manifestation of motor phenomena without significant loss in consciousness; while not an exhaustive list, PNED can be precipitated by events such as; toxic and metabolic disturbance, transient ischemic attack (TIA), and stroke. (source)
Since autism is a psychiatric label that that does not provide information on known cause, and since it is a label utilized to inform on such a wide and diverse population as far as intellectual ability, function and unique presentation of features (per each individual) - it remains difficult to interpret the neurology behind why each affected individual is displaying symptoms related to seizure or movement disorder. EEG might be considered the sole diagnostic tool to verify many seizure activities. However, many with the autism label are difficult to test because of their behaviors and may have seizure involvement from neurological cause aside of typical seizure disorder. Difficulty in assessment was experienced in my daughter's case upon worsening of autism during puberty. However, EEG was attempted:
The video EEG was successful in that they were able to record many of Sarah’s episodes. They did rule out actual seizures. Most of the episodes they recorded involved the weird eye gaze, with verbal utterances and head movements. The report alluded to diagnoses of autism spectrum, schizoid features, multiple repetitive activities, and absence spells. The report said that the behavioral changes were believed to be secondary to schizophrenia. The neurologist followed up and pointed to the fact that Sarah had both auditory and visual hallucinations during differing hospital visits. Her thoughts were Autism, and rule out schizophrenia; that required an inpatient stay in the psychiatric unit. (Hello Dr Wells)
Throughout a long process of attempts in treatment the above cited manifestations were eventually thought to be the result of a rare variant of periodic catatonia. After that, through happenstance - MRI indicated that a stroke had occurred; and the area of the brain involved had been known to be associated with the type of catatonia exhibited.
With regard to catatonia, it is prominent in patients with epilepsy; however, there are catatonic presentations that are absent of detected EEG activity; and further, EEGs are described to be difficult to interpret because of muscle rigidity producing artifacts that are present during a catatonic spell. Catatonic events seem to involve neural networks underlying termination of movement in contrast to those underlying initiation of movement (link). Problems with termination of movement were present in the above cited scenario, and she was hopeless to do battle with the spells that would take her over. As further example:
Behavior cards coming from the school dramatically increased. The episodes emerged at school and at home. They ebbed and they flowed seeming to do whatever they wanted, whenever they wanted. They seemed like a meditative state that took over Sarah. They were almost always distressing and upsetting to her. Her will seemed to want to control the problem, but will was not enough. She definitely tried fighting the onset of them, but was hopeless to do battle and stop them. (Hello, Dr. Wells)
For those within the autism population, consideration into the implications of seizure will continue to prove a most complex proposition for the researchers and doctors - due to the numerous variables involved with all the subset groups who are represented by the autism label. And also due to the many differing types of seizures with multiple causations.
By the way, Sarah (the above cited example subject) is doing fine now; graduating from public high school soon. Kudos to all who endeavored to stick by her through thick and thin.