Diagnosis and investigation of Bell's Palsy

This article describes about the Diagnosis and investigation of Bell's Palsy. Also read to know more about Pure tone audiometry and Electro diagnostic test and Topognostic tests for Bell's Palsy.

Bell's palsy the commonest form of facial paralysis is diagnosed mostly on history and features which suggest a sudden onset probably after exposure to cold or may be due to trauma which may cause transudation leading to compression of facial nerve. The details of the feature is given at Bell's Palsy.

Diagnosis of Bell's Palsy

Diagnosis of Bell's palsy is evident from proper history and clinical features, negative finding in ears as there is no abnormality. Test for taste and lacrimation as taste will be intact and lacrimation present, There may be lower motor neuron type of paralysis. The investigations mainly required is myography, stapedial reflex test and nerve excitability test. It is done by the following.

Investigations for Bell's palsy

The investigations required are pure tone audiometry, electro diagnostic tests and topognostic tests.

Pure tone audiometry

Pure tone audiometry is done by tuning fork to detect the air conduction and bone conduction of sound and in Bell's palsy it is normal.

Electro diagnostic test

Electrodiagnostic test is done to test the nerve conduction and condition of the muscle supplied by those nerves. The test includes

Electromyography (EMG)- This is done to check the condition of muscles and its strength.

Strength duration curve (SD curve)

Nerve excitability test - In nerve excitability test we see that on increasing the threshold on the side pof palsy by 4 to 5 m.a , then the nerve function is severely impaired.

Electro neuronography - Electro neuronography or (ENoG)is the most advanced and modern test and detects the number of nerves affected. It also helps in assessing the mode of treatment as if more than 95% degeneration of nerve is there after 2 weeks of onset then medical treatment may not be effective and surgical decompression may be required.

Topognostic tests for Bell's palsy

Topognostic tests are done to localize the site of lesion. This test includes-

Schirmer's test - Schirmer test also called lacrimal test is done to detect the geniculate ganglion is normal or affected.

Salivary flow tests.

Gustometry - It is done to test the pathway of taste and detect whether the branch of facial nerve called chorda tympani is incolved or not. It can be done by electrical method or by topical method.

Stapedial reflex - This is done to detect the nerve involvement proximal or distal to stapedius muscles.

Thus the proper diagnosis can give an idea of extent and site of nerve involvement, treatment is mostly conservative but surgery may require in some cases. Details can be see at Treatment of Bell's Palsy.

Reference: http://dr-healthguide.blogspot.com


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