Focal inflammatory myositis of the paraspinal neck muscles
by Jaiganesh Manickavasagam, MRCS (Edin), Sam Majumdar, FRCS (ORL–HNS), and Abir K. Bhattacharyya, FRCS (ORL)

A 33-year-old Asian woman presented to the emergency department after a sudden onset of neck stiffness and general malaise earlier that evening. Examination revealed low-grade pyrexia (38°C) and the presence of a diffuse, minimally tender, nonfluctuant swelling that measured approximately 6 × 6 cm in the right suboccipital region.

Hematologic and serologic investigations demonstrated an elevated white blood cell count (22.4 × 10⁹/L) and an elevated C-reactive protein level (139.8 mg/L). Other biochemical test results, including the creatine phosphokinase (CPK) level, were within normal limits. Ultrasonography of the neck did not detect any collection suggestive of an abscess or lymphadenopathy. Magnetic resonance imaging (MRI) of the neck demonstrated focal inflammatory myositis of the paraspinal muscles with intact facial planes (figure). Fine-needle aspiration cytology of the suboccipital mass was reported as serous fluid containing inflammatory cells, including neutrophils.

Swelling and marked enhancement of the right-sided paraspinal muscles (arrows) are seen on various MRI views: T1-weighted axial (A), gadolinium-enhanced T1-weighted coronal (B), gadolinium-enhanced T1-weighted axial (C), and T2-weighted coronal (D).

 The patient was started on intravenous prednisolone (8 mg three times daily) and regular analgesia (acetaminophen and ibuprofen). The following day, a marked reduction in swelling and an improvement in the range of neck movements were noted. The patient continued to improve daily, and she was discharged on hospital day 3 with a 5-day course of oral prednisolone. At the 1-month follow up, the swelling had completely resolved. Findings on repeat biochemical and immunologic investigations—including measurements of rheumatoid factor, antinuclear antibodies, and CPK—were within normal ranges.

Focal myositis, which was first described by Heffner et al1 in 1977, is a self-limiting, localized inflammation of skeletal muscles of unknown etiology, although a viral etiology and muscle denervation have been implicated in its pathogenesis. Focal myositis was initially described as affecting the skeletal muscles of the lower extremities, but since then 23 cases of focal myositis of the head and neck region have been reported in the literature. In the head and neck, several different muscles may be affected: the sternocleidomastoid, mylohyoid, digastric, temporalis, tongue, and perioral group muscles.2,3 The sternocleidomastoid muscle is the most commonly affected muscle in the head and neck; patients typically present with torticollis.

Clinically, focal myositis may present as a rapidly enlarging, painful swelling of a skeletal muscle. Systemic symptoms or signs may be minimal or absent, a finding that differentiates focal myositis from an early, localized form of polymyositis.4 Macroscopically, the affected muscle is often pale, rubbery, and edematous, with no involvement of the fascia, tendon, or overlying skin.5 The acute histologic picture is characterized by infiltration of necrosed and regenerating muscle fibers by inflammatory cells such as lymphocytes.4 In chronic cases, there is new connective tissue deposition in the endomysium and perimysium. The differential diagnosis includes myositis ossificans, proliferative myositis, nodular fasciitis, and sarcoma. In most cases, the white blood cell count and the erythrocyte sedimentation rate are either normal or only minimally elevated; CPK and aldolase levels are invariably within normal limits.

The diagnosis of focal inflammatory myositis is enhanced by a high level of suspicion. The diagnosis is made on cytologic or histopathologic findings and aided by high-quality imaging. The inflammatory nature of this entity would seem to support a therapeutic role for steroids; indeed, in most cases, steroids are effective in rapidly reducing the lesion.3,6 Despite its aggressive presentation, focal myositis is a benign condition that resolves spontaneously or with steroid treatment.

From the ENT Department, Royal Hallamshire Hospital, Sheffield, U.K. (Mr. Manickavasagam and Mr. Majumdar), and the ENT Department, Whipps Cross University Hospital, London (Mr. Bhattacharyya).

References

1.        Heffner RR Jr., Armbrustmacher VW, Earle KM, Focal myositis. Cancer 1977; 40 (1): 301–6.

2.        Josephson GD, de Blasi H, McCormick S, et al. Focal myositis of the sternocleidomastoid muscle: A case report and review of the literature. Am J Otolaryngol 1996; 17 (3): 215–17.

3.        Naumann M, Toyka KV, Goebel HH, et al. Focal myositis of the temporal muscle. Muscle Nerve 1993; 16 (12): 1374–6.

4.        Heffner RR Jr., Barron SA. Polymyositis beginning as a focal process. Arch Neurol 1981; 38 (7): 439–42.

5.        Maheshwar AA, Douglas-Jones AG, Cuddihy PJ. Rapidly enlarging lump in the neck: Is it a tumour? J R Coll Surg Edinb 2000; 45 (5): 339–41.

6.            Georgalas C, Kapoor L, Chau H, Bhattacharyya A. Inflammatory focal myositis of the sternomastoid muscle: Is there an absolute  indication for biopsy? A case report and review of the literature. Eur Arch Otorhinolaryngol 2006; 263 (2): 149–51.