Yawning is an arousal reflex thought to be generated in the brainstem reticular formation to counteract brain hypoxia; it may precede vasovagal syncope. Excessive or pathological yawning (chasm) is compulsive, repetitive yawning not triggered by physiological stimuli, such as fatigue or boredom. Known associations of yawning include:
Tumors of the 4th ventricle, frontal lobes Electroconvulsive therapy Postthalamotomy
Drugs (valproate, imipramine) Neuroleptic withdrawal
Parkinson’s disease, progressive supranuclear palsy, restless legs syndrome, pseudobulbar palsy of motor neurone disease
Although the mechanisms are uncertain, yawning may represent a disturbance of dopaminergic transmission. Levodopa may help.
Leonhardt M, Abele M, Klockgether T, Dichgans J, Weller M. Pathological yawning (chasm) associated with periodic leg movements in sleep: cure by levodopa. Journal of Neurology 1999; 246: 621-622 Williams DR. The yawning reflex: an upper motor neuron sign in amyotrophic lateral sclerosis. Neurology 2000; 55: 1592-1593