Some patients suspected of having bilateral parotid gland enlargement actually have hypertrophy of the masseter muscles. The hypertrophy is usually caused by long-term use of the muscles.


Clinical features:

(1) The patient is usually a young adult without dental pain..

(2) The patient has a longstanding cause for muscular hypertrophy (see below).

(3) The parotid glands are normal on imaging studies, while the muscles are enlarged.

(4) There is a normal flow of saliva.

(5) The parotid duct is normal on sialography.

(6) The parotid glands are not swollen.

(7) The parotid glands are not tender.

(8) The face when viewed from the front has a rectangular configuration.

(9) The teeth may show erosions or signs of abrasion.


Causes of masseter muscle hypertrophy:

(1) persistent clenching of the teeth

(2) bruxism (grinding the teeth)

(3) persistent gum chewing


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