Unilateral temporal muscle hypertrophy: A rare clinical entity. (Original Article).

Abstract

Isolated unilateral temporal muscle hypertrophy is a rarely reported clinical entity with an unclear etiology. Consideration of a broad differential diagnosis combined with a detailed histologic and radiologic work-up will help the physician diagnose the underlying pathology. We report a new case of this uncommon entity, and we review the pertinent literature.

Introduction

Unilateral temporal muscle hypertrophy is a rare phenomenon with an unclear etiology. To date, only three cases have been previously described in the Western literature. (1-3) The first published description of bilateral masseter and temporal muscle hypertrophy is credited to Legg in 1880. (4) Since then, multiple cases of bilateral masticatory muscle hypertrophy have been described. (5)

The underlying etiology of temporal muscle hypertrophy has been attributed to chronic bruxism, masseteric hyperfunction, and parafunctional jaw habits. (1, 2, 5) However, in the rare case of unilateral hypertrophy, the possibility of more serious clinical etiologies must be entertained. In this article, we report a new case of isolated unilateral temporal muscle hypertrophy, we discuss its associated clinical implications, and we review the scant literature on this rare entity.

Case report

A 45-year-old black man came to our clinic with a 1-year history of recurrent headache and an enlarging mass on the left side of his head. He denied recent head trauma, surgery, and bruxism. His medical history was significant only for quiescent cutaneous sarcoidosis. Examination revealed a diffuse, nontender enlargement of the left temporal muscle, but no associated lymphadenopathy. The contralateral temporal and masseter muscles were of normal size. Inspection of the patient's dentition revealed normal occlusion and no evidence of abnormal wear.

The patient's complete blood count and erythrocyte sedimentation rate were normal. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a homogeneous enlargement of the left temporal muscle and prominent underlying vascularity (figure). An incisional biopsy carried out with local anesthesia and intravenous sedation showed normal temporal muscle histology.

The patient was not interested in cosmetic surgery, and he declined any further intervention once the diagnosis of benign temporal muscle hypertrophy was confirmed.

In the evaluation of suspected temporal muscle hypertrophy, measurement of the complete blood count and erythrocyte sedimentation rate and imaging with CT and/ or MRI are essential. MRI is preferred for soft-tissue delineation, while CT better demonstrates bony involvement. A definitive diag nosis is based on an incisional biopsy of the temporal muscle, which is obtained by making a small postauricular incision with the patient under local anesthesia and intravenous sedation.

Discussion

Most cases of masticatory muscle hypertrophy described in the literature are bilateral; parafunctional jaw habits have been cited as a common etiology. (2) In the rare case of isolated unilateral temporal muscle hypertrophy, attention should be focused on the diagnosis of any underlying pathology, especially in a patient who has no medical history or examination that is suggestive of bruxism or masticatory hyperfunction. (1, 5) The differential diagnosis includes benign muscle hypertrophy, idiopathic inflammatory myopathy, proliferative myositis, muscular dystrophy, lipomatosis, liposarcoma, rhabdomyosarcoma, and infiltrative leukemias and lymphomas. In our patient, we also considered a diagnosis of recurrent sarcoidosis.

Once the diagnosis is confirmed, attention can then be directed toward treatment. Multiple cosmetic options exist to treat benign masticatory muscle hypertrophy, including muscle excision and myosuction. More recently, injection with type A botulinum toxin has also been used. (3,6,7) Alternatively, patients might elect to undergo no further treatment. In cases where an underlying pathology is identified, treatment is based on the respective diagnosis.

References

(1.) Wilson PS, Brown AM. Unilateral temporalis muscle hypertrophy: Case report. Int J Oral Maxillofac Surg 1990;19:287-8.

(2.) Serrat A, Garcia-Cantera JM, Redondo LM. Isolated unilateral temporalis muscle hypertrophy. A case report. Int J Oral Maxillofac Surg 1998;27:92-3.

(3.) Isaac AM. Unilateral temporalis muscle hypertrophy managed with botulinum toxin type A. Br J Oral Maxillofac Surg 2000;38:571-2.

(4.) Legg JW. Enlargement of the temporal and masseter muscles on both sides. Trans Pathol Soc Lond 1880;31:361-6.

(5.) Harriman DG. The histochemistry of reactive masticatory muscle hypertrophy. Muscle Nerve 1996; 19:1447-56.

(6.) von Lindern JJ, Niederhagen B, Appel T, et al. Type A botulinum toxin for the treatment of hypertrophy of the masseter and temporal muscles: An alternative treatment. Plast Reconstr Surg 2001;107:327-32.

(7.) Morselli PG. Temporalis muscle hypertrophy: A new plastic surgery procedure. Plast Reconstr Surg 2000;106:1156-61.

From the Department of Otolaryngology--Head and Neck Surgery, Brooke Army Medical Center, Ft. Sam Houston, Tex.

Reprint requests: Capt. Thomas R. Lowry, MD, Department of Otolaryngology--Head and Neck Surgery, wilford Hall Medical Center, 2200 Bergquist Dr., Suite 1, MCSR, Lackland AFB, TX 78236-5300. Phone: [phone]; fax: [phone]; email: [e-mail]