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  • Updated 09.29.2020
  • Released 10.11.2014
  • Expires For CME 09.29.2023

Pathologic yawning: neurologic aspects

Introduction

Overview

Excessive yawning is increasingly being recognized as a manifestation of neurologic disorders. Several neurotransmitters and neurohormones are involved in the regulation of yawning. Several areas in the brain are implicated, but no definite center for yawning has been identified. According to the thermoregulatory theory of yawning, its function is to cool the brain, and excessive yawning may be a symptom of conditions that increase brain temperature. Differential diagnosis requires consideration of various disorders linked to excessive yawning. Treatment involves addressing the basic disorder. Propranolol can reduce the severity of yawning.

Key points

• Previously considered to be a sign of boredom and drowsiness, excessive yawning is now increasingly linked to neurologic disorders.

• Several neurotransmitters and neurohormones are involved in the neuropharmacologic regulation of yawning.

• According to the thermoregulatory theory of yawning, its function is to cool the brain, and excessive yawning may be a symptom of conditions that increase brain temperature.

• Several drugs are reported to induce yawning, and this should be taken into consideration in the differential diagnosis.

• Propranolol, a beta blocker, has been found to reduce the severity of yawning.

Historical note and terminology

A yawn is an involuntary sequence of mouth opening, retraction of the tongue, deep inspiration, brief apnea, and slow expiration. Excessive yawning is defined as 3 or more yawns per 15 minutes.

Since antiquity, yawning has attracted a moderate interest among philosophers, psychologists, physiologists, and physicians. Hippocrates listed yawning as 1 of the useful “natures,” and Darwin mentioned it in connection with emotional behavior (39). Yawning was described as a tic-like disorder in a monograph (31).

Historically, yawning has been associated with drowsiness and boredom, but this age-old belief is changing as newer studies have shown the significance of yawning in physiology and as a symptom of various disorders (21). It is ancient from an evolutionary point of view as it is observed in all classes of vertebrates and has an early onset in humans in utero. Yawn duration is a predictor of mammalian brain weight and cortical neuron number, and primates have longer and more variable durations of yawning compared with other mammals (14).

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