Case Report

Isolated Unilateral Temporalis Muscle Hypertrophy: A Case Report and Review of the Literature


  • Ahmet Öğrenci
  • Orkun Koban
  • Onur Yaman
  • Sedat Dalbayrak

Received Date: 10.05.2017 Accepted Date: 13.11.2017 Med Bull Haseki 2018;56(2):165-168

Isolated unilateral temporalis muscle hypertrophy is a very rare pathology that nine cases have been reported to date. We report the 10th case of this rare condition and a review of the literature. Swelling of the masticatory muscles may be isolated or may be present together. Reactive and nonreactive causes are accused for the etiology. Significant pathologies accompany non-reactive causes. Some reactive causes are parafunctional jaw habits, excessive gum chewing, and bruxism. Biopsy is the gold standard method of differentiating between reactive and nonreactive causes. The treatment can be tailored according to the biopsy results. Medical treatment, surgery and Botulinum toxin A (BtA) injection are available to treat the reactive causes. BtA therapy is the most effective option. There is no clear information in the literature about the size of swelling in untreated patients. We did not apply an extra treatment after the patient’s biopsy except nonsteroidal antiinflammatory drug. The patient is being followed up with no increase in swelling.

Keywords: Hypertrophy, masticatory, swelling, temporalis muscle


The management of temporalis muscle hypertrophy depends on its origin. It is necessary to differentiate between reactive and non-reactive hypertrophy. The process is known in case of reactive hypertrophy. In non-reactive hypertrophy, it is necessary to investigate the cause. Up to now, there have been nine reported cases of isolated unilateral temporalis muscle hypertrophy (IUTMH) in the literature. Here, we present a case of IUTMH and a review of the literature.


A 35-year-old female patient was admitted to our clinic with painless swelling in the right temporal region (Figure 1). The patient had no complaints other than cosmetic concerns. She had no chronic disease. The swelling started three months ago and has been stable for the last one month.

There was no asymmetry on the face of the patient. There was no skin abnormality. There was no findings in oral, dental and jaw joint (temporomandibular: TM) examination. There was no other complaint. The patient had no bruxism and there was no history of trauma. During this time, she had used anti-inflammatory drugs but the swelling has increased. Routine blood tests were all within the normal limits. Contrast-enhanced cranial magnetic resonance imaging showed a non-contrasting muscle structure which appeared isointense with normal muscle. (Figure 2, 3) The right temporal muscle was clearly hypertrophic with respect to the left. There was no intracranial pathology.

The other masticatory muscles groups were symmetric. There were no bone pathology on cranial computed tomography and x-ray images. TM joint appeared normal. The patient underwent biopsy for diagnostic purposes. A biopsy was performed under local anesthesia with a small incision and the result was reported as normal muscle tissue (Figure 4).

The patient refused Botulinum toxin A (BtA) treatment that we recommended after biopsy. Now the patient is in the 3rd year and there is no increase in the muscle mass.

To our knowledge, this is the first case of isolated unilateral temporal hypertrophy reported in Turkey.

The permission has been got from the patient for the article.


The first case of masticatory muscle hypertrophy was reported by Legg (1) in 1880.

Masticatory muscle hypertrophy may affect the masseters, temporalis and pterygoid muscles and is usually bilateral (2-4).

Unilateral appearance is usually less common. IUTMH was published long after the report of masticatory muscle hypertrophy. The first report of IUTMH was published by Wilson and Brown (5) in 1990.

To the best of our knowledge since then, nine cases have been reported (Table 1). The case presented here is the 10th in the world and the first in Turkey.

Painful or painless swelling and headache are generally the first presentation complaints. No apparent side dominance has been reported in the literature.

The etiology is not clear, however, both reactive and nonreactive causes are accused of causing. Non-reactive causes include genetic problems, myopathies, inflammatory or infectious causes, vascular malformations, myositis, neoplastic processes, and metastases (4,6-8).

Hypertrophy of the temporal region may be seen in bone deformities after craniofacial trauma, in those who have joint problems and dental problems.

Regarding the reactive causes, patients with parafunctional jaw habits, excessive gum chewing habits, and bruxism are at risk. Oral-dental examination should be performed. Dental wear may be help to diagnose bruxism. It is also stated that psychogenic disorders can be the trigger if there is no cause (6). However, there is no exact etiology identified. As a matter of fact, we could not find any reason in our patient.

Our patient had no parafunctional habits. We could not detect any abnormality in the physical examination, radiological evaluation and laboratory tests.

The diagnosis is confirmed by biopsy (4,7-9). Biopsy is a quick, simple and low-risk procedure for identifying reactive or nonreactive causes. No matter how many radiological or laboratory tests are performed, they will not replace the data that the biopsy will yield. Biopsy is required in all patients with temporalis muscle hypertrophy.

Katsetos et al. (7) and Harriman (6) investigated histochemistry of mascitory muscle hypertrophy and have argued that the dominance of type 1 myofibrils was the cause. Katsetos et al. (7) stated that the diameter of type 1 fibers was larger than that of type 2 fibers, and there was not myopathic view on pathological examination.

After diagnosis, treatment should be planned according to the etiology. If it is related with nonreactive processes, the primary reason should be treated. However, for a reactive cause, when the biopsy reveals normal muscle tissue, the treatment may vary. If the patient has behaviors that may cause hypertrophy in this area, it can be suggested to reduce them and patient can be followed up. Psychological reasons should be treated; it will be difficult to achieve success with other therapies without treating psychological causes. Analgesics, non-steroidal anti-inflammatory (NSAI) drugs, acetaminophen, or muscle-relaxant drugs can be used (7). BtA therapy can be performed in the next period or muscle excision can be done as a more invasive treatment option (10). Surgical management is considered in patients not benefiting from other methods, but it should not be the first treatment option. Trismus, fibrosis, hematoma and recurrence may develop after surgery (10-12). BtA injection is a more rational treatment option at this point. Although BtA is more costly than the other treatments, it causes paralysis in the muscle structure, reduces tonus, and causes atrophy and decrease in headache (13). Periodic BtA injections may be required (8). In botulinum toxin treatment BtA is recommended due to the duration of influence (14). Botulinum F has shorter effect compared to BtA.

In our case, we ordered NSAI based on the biopsy result. We recommended BtA treatment since the patient did not benefit from medical agents, however, the patient refused the treatment. Thus, we follow up the patients with the size of mass. No progression or regression was observed during the 3rd year of follow-up.

We assume that temporal hypertrophy may continue to a certain point and then may remain stable. In our theory, the increased pressure in the temporal region prevents growth in muscle mass. Therefore, patients with temporal hypertrophy can be followed up after biopsy if there are no serious symptoms.

IUTMH is very rare cause of swelling of the temporal region. If there is not a non reactive cause, it is a reactive hypertrophy. Radiographic images show normal results or normal intensity of the other muscles. In the differential diagnosis, biopsy should be performed. Various treatments, especially Botulinum toxin, can be ordered after biopsy, or the patient can be followed up if there is no evidence of an increase in the size of the mass, and there is no serious symptom.

Authorship Contributions

Surgical and Medical Practices: A.Ö., O.K. Concept: A.Ö., O.K. Design: A.Ö., O.Y. Data Collection or Processing: A.Ö., O.K. Analysis or Interpretation: A.Ö., O.K., O.Y., S.D. Literature Search: A.Ö., O.Y. Writing: A.Ö.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.

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