Paroxysmal attack
They are usually associated with multiple sclerosis or pertussis, but they may also be observed in other disorders such as encephalitis, head trauma, stroke, autism, asthma, trigeminal neuralgia, breath-holding spells, epilepsy, malaria, tabes dorsalis, and Behçet's disease, paroxysmal nocturnal hemoglobinuria (PNH).[3] Paroxysmal attacks in various disorders have been reported extensively, and ephaptic coupling of demyelinated nerves has been presumed as one of the underlying mechanisms of this phenomenon.This is supported by the presence of these attacks in multiple sclerosis and tabes dorsalis, which both involve demyelination of spinal cord neurons.Exercise, tactile stimuli, hot water, anxiety and neck flexion may provoke paroxysmal attacks.They are typically different from other transient symptoms by their brevity (lasting no more than 2 minutes), frequency (from 1–2 times/day up to a few hundred times/day), stereotyped fashion and excellent response to drugs (usually carbamazepine).