An Extremely Rare Condition: Unilateral and Isolated Temporalis Muscle Hypertrophy.

Unilateral and isolated temporalis muscle hypertrophy is an extremely rare condition causing cosmetic problems and pain in the temporal region. Up to date, 8 isolated and unilateral cases were reported in the English literature. In this article, the authors report 2 new cases of unilateral isolated temporal muscle hypertrophy.

CASE REPORT

Two patients applied to our clinic with a gradual swelling in the right side of scalp and temporal region. One of the patients was a 23-year-old man and the other was a 38-year-old woman. They had noticed the swelling on their temporal regions in a period of 7–10 months. The patients had no history of bruxism, temporomandibular joint disease, surgery, or any trauma. In the physical and neurological examination, large, readily palpable and soft diffuse mass was observed in the right scalp and temporal region of the patients (Fig. 1A). Magnetic resonance imaging (MRI) and computed tomography (CT) studies revealed homogenous enlargement of only right temporalis muscle without any underlying pathology and other intracranial abnormality (Fig. 1B–D). With the results of clinical examination and radiologic findings, the diagnosis was isolated unilateral temporal muscle hypertrophy. One of the patients was treated by surgical reduction of the muscle but the other patient consented to neither surgical nor medical treatment of the disease.

Fig. 1.

A, Patient before the treatment. B, No bony pathology was able to be verified with CT study. C and D, CT and MRI images show homogenous enlargement of the right temporal muscle hypertrophy.

DISCUSSION

Since the first report of masticatory muscle hypertrophy, a number of cases have been reported with this condition in the literature.[1-3] Unilateral masseter and other masticatory muscle hypertrophy are uncommon conditions, and the majority of the reports in the literature involve masseter muscle hypertrophy. In addition, masticatory muscle hypertrophy can occur in a variety of combinations of hypertrophy affecting the temporalis, masseter, and others.[3] This condition is generally bilateral and occurs with parafunctional jaw habits.

Wilson and Brown[4] published the first report of isolated temporalis muscle hypertrophy in 1990. To date, only 8 cases of the condition have been reported.[1] To our knowledge, the patients presented in this article are 2 new cases of isolated and unilateral temporalis muscle hypertrophy in the literature. The cause of temporalis muscle hypertrophy is unclear, but compensatory and stress hypertrophy has been assumed in most of the cases.[5] Our cases had no history of temporomandibular joint disease, bruxism, surgery, or any trauma. Although the previous reports suggested that the cases had painful swelling and headaches and these reports, furthermore, proposed that there may be a be potential link between the onset of the headache and isolated unilateral temporalis muscle hypertrophy, our cases had no headaches or any pain with the rare condition of their temporal regions. Therefore, they applied to our clinic to solve only their cosmetic problems.

The diagnosis of the condition is usually established by careful physical examination and medical history. CT, MRI, or ultrasound can be helpful to show enlargement of the muscles.[6] MRI is the preferred method for evaluating soft-tissue abnormalities. The imaging methods and clinical examination showed that the patients had homogenous enlargement of the right temporal muscles without other intra- or extra-cranial abnormalities. Treatment options for this condition are symptomatic treatment with analgesics in those patients with pain, muscle reduction surgery, and/or Botox injections.[7,8] Surgical reduction of the muscle or Botox injection was offered to the patients with some advantages of injection method. One of the patients asked for the surgical treatment but the other patient did not want to take any treatment and she has been observed clinically.

PATIENT CONSENT

The patient provided written consent for the use of his image.