Bell's Palsy

                                                                        Bell's Palsy.

                                                              PKGhatak, MD

Sudden onset of paralysis of one half of the entire face is called Bell's palsy. In medical terms, it is a lower motor neuron paralysis of the facial muscles of one side. Bell is Sir Charles Bell of Scotland (1774-1842). He was a Neuroanatomist cum surgeon. He gained first-hand knowledge of facial injuries while working as a surgeon in the Battle of Waterloo (1815).

The term “Palsy” is derived from the Anglo-French word “Palseie”. The Greek word “Paralysis” means loosening, it is derived from the verb “Paralysia” meaning to disable/ enfeeble.

Although Sir Charles Bell was the first to provide the anatomic basis for the condition that bears his name, in recent years researchers have shown that other European physicians provided earlier clinical descriptions of peripheral cranial nerve 7 palsy. History of facial distortion by Greek, Roman, and Persian physicians, culminating in Razi's detailed description in al-Hawi (9^th century CE). Razi distinguished facial muscle spasm from paralysis, distinguished central from peripheral lesions, gave the earliest description of loss of forehead wrinkling, and gave the earliest known description of bilateral facial palsy. In doing so, he accurately described the clinical hallmarks of a condition that we recognize as Bell palsy.

Dr. Bell, of Bell's palsy fame, had suffered a right sided facial paralysis of his own before he became famous.

A question:

Mona Lisa. Whoever has seen the world famous painting of Mona Lisa by Leonardo da Vinci must have pondered what that smile is all about. At a conference in Vienna, a group of researchers said Mona Lisa had right facial paralysis during her pregnancy and recovered after childbirth.

Anatomy of motor nerve of the face.

The above diagram is an outline of the 7^th nerve motor nerve supply to facial muscles. The pyramidal cortex sends signals to the upper division nucleus of both 7^th cranial nerve motor nuclei. (Facial nerve). The lower division of 7^th nerve motor nucleus, on the other hand, receives signals from one side only (contralateral side). In a stroke due to pyramidal cortex disease, only contralateral side of the face is paralyzed and muscles of forehead remain functional.

In Bell's palsy, the entire facial muscles, including the forehead muscles, are paralyzed.

Common causes of Bell's Palsy.

Chill wind blowing against the face in a long drive.

Herpes zoster. Herpes simplex. Epstein-Barr and COVID-19 virus infection.

Lyme disease from spirochete infection.

Acoustic neuroma (tumor of 7^th nerve fibers in the ear), Schwannoma (cells that make myelin) and cholesteatoma.

Injury to the Facial nerve.

During surgery of the parotid gland, a Knife wound behind the ear. Fracture of the base of skull. Nerve block during dental procedures.

Pregnancy and diabetes mellitus.

Critical areas of the path, the Facial nerve, where disease is likely to produce Bell's palsy.

1. Narrow canal inside the Temporal bone. 

2. The neck of the mandible.

 3.Parotid salivary gland.

Causes of paralysis of the Lower part of the face only.

A.  Strokes from blocked blood supply to the mid brain.

B. Blood clot emboli originate from heart valves, heart chambers, or atrium in atrial fibrillation.

C. Infectious vegetation from heart valve or artificial valve disease.

D. Intracerebral bleeding from use of anticoagulants.

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