While idiosyncratic and self-referential content often make delusions impossible to share with others, Dr. Pierre suggests that it may be more helpful to emphasize the level of conviction, preoccupation, and extension of a belief rather than the content of the belief when considering whether a belief is delusional.It is important to distinguish true delusions from other symptoms such as anxiety, fear, or paranoia. To diagnose delusions a mental state examination may be used. This test includes appearance, mood, affect, behavior, rate and continuity of speech, evidence of hallucinations or abnormal beliefs, thought content, orientation to time, place and person, attention and concentration, insight and judgment, as well as short-term memory.Johnson-Laird suggests that delusions may be viewed as the natural consequence of failure to distinguish conceptual relevance. That is, irrelevant information would be framed as disconnected experiences, then it is taken to be relevant in a manner that suggests false causal connections. Furthermore, relevant information would be ignored as counterexamples. Definition
Although non-specific concepts of madness have been around for several thousand years, the psychiatrist and philosopher Karl Jaspers was the first to define the four main criteria for a belief to be considered delusional in his 1913 book General Psychopathology. These criteria are:

certainty (held with absolute conviction)
incorrigibility (not changeable by compelling counterargument or proof to the contrary)
impossibility or falsity of content (implausible, bizarre, or patently untrue)
not amenable to understanding (i.e., belief cannot be explained psychologically)Furthermore, when beliefs involve value judgments, only those which cannot be proven true are considered delusions.
Congenital bilateral perisylvian syndrome (CBPS) is a rare neurological disease characterized by paralysis of certain facial muscles and epileptic seizures. Signs and symptoms
Signs and symptoms of CBPS typically appear in infancy or at birth, but can appear later in childhood. These include facial diplegia (paralysis on both sides), facial muscle spasms, pseudobulbar palsy, dysarthria (difficulty speaking), difficulty chewing, dysphagia (difficulty swallowing), epilepsy, and intellectual disability. Epileptic seizures in individuals with CBPS are different between individuals and can vary between episodes. Pathophysiology
Though the underlying cause of CBPS is unknown, it is thought to arise from improper migration of neuroblasts (neuronal stem cells) to the cerebral cortex in the embryonic brain. This causes the layers of the cerebral cortex to not form properly, and too many small folds (gyri) to form on the surface of the brain. This condition is called bilateral perisylvian polymicrogyria. The sulci, deep grooves on the brain, may also not form correctly. Cranial nerves are affected and cause muscle paralysis and spasms in the face and throat. Diagnosis
Several disorders may appear similar to CBPS and need to be distinguished in the process of diagnosing CBPS. These include pachygyria, double cortex syndrome, and lissencephaly, all of which are classified along with CBPS as neuronal migration disorders. Diagnostic tests for CBPS include electroencephalograms, CT scanning, and magnetic resonance imaging. Treatment
CBPS is commonly treated with anticonvulsant therapy to reduce seizures. Therapies include anticonvulsant drugs, adrenocorticotropic hormone therapy, and surgical therapy, including focal corticectomy and callosotomy.