Neuropsychiatric Symptoms of Epilepsy

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N. Adachi and N. Akanuma
Introduction
Links between psychoses and epilepsy have been recognized and documented since
ancient times [ 1 ]. The position of epilepsy in the field of psychiatry has notably
changed, as diagnosis and treatment for psychoses has advanced. Epilepsy was considered
a mental disorder/insanity; therefore, no separate entity as “psychosis in
epilepsy” was established until the early twentieth century [ 2 ]. Today, the DSM-5
[ 3 ] includes specifics of psychoses in epilepsy with commonly used subclassifications
under psychotic disorder due to another medical condition (code 293.8). We
recognize that the prevalence of psychoses is higher in people with epilepsy than in
the general population [ 4 – 6 ]. Their vulnerable factors are related to both epilepsy
and generic features such as genetic predisposition to psychoses and intellectual
functioning. Bidirectional relationships between epilepsy and psychoses in their
genesis are also observed [ 7 – 9 ].
During the era before modern psychiatry, psychoses were conditions with anomalous
behavior, including hallucinations, delusional ideas, elated mood, psychomotor
excitement, impaired consciousness, dissociation, or dementia. In the middle of
the nineteenth century, it became possible to recognize psychotic symptoms that
occurred following obvious cerebral pathology or damage, such as neurosyphilis
and wartime head injury [ 2 ]. These psychoses were called “organic psychosis” in
contrast to “functional psychosis” (the condition without apparent brain damage or
disorders), including what we now call schizophrenia. At around the same period of
time, psychoses were defined as a condition occurring under clear consciousness,
excluding symptoms and behavior under clouded consciousness (due to cerebral or
systemic abnormalities), which were termed “delirium” [ 10 , 11 ].
Understanding the psychopathology of psychoses was dramatically increased in
the early twentieth century when German psychiatrists [ 12 , 13 ] established a methodology
for mental state examination and its description for patients treated in long- stay
hospitals. Delusions and hallucinations were at the center of these studies.
Classification of psychoses, together with other mental disorders, also progressed by
using psychopathology, etiology, course of illnesses, and their prognosis: the foundation
of modern classifications that we currently use [ 3 , 14 ]. It was generally accepted
that the psychopathology of the delusions or hallucinations per se did not have a
diagnostic value for a specific condition, although certain symptoms tended to be
observed more frequently in one condition than the others. It was also understood that
both delusions and hallucinations could be seen in the nonclinical population [ 15 ].
Since the operational diagnostic criteria (e.g., DSM [ 3 ] and ICD [ 14 ]) became
common for the use of research and clinical practice in 1980s, abnormal thoughts
and perceptions, mainly delusions and hallucinations, were seen as the core symptoms
of psychoses. These symptoms were coined by Crow [ 16 ] “positive symptoms”
of psychoses, while other symptoms, including blunted affect and abulia,
were called “negative symptoms.” In the recently published DSM-5 [ 3 ], a wider
range of symptoms has been added to the diagnostic criteria for psychotic disorders,
which include formal thought disorders, grossly disorganized or abnormal motor
behavior (including catatonia), and negative symptoms.