Teaching NeuroImages: Pterygoid myositis mimicking giant cell arteritis

Summary

Terminology

Original

  • 51yo F
  • c/c
    • headache
    • tenderness Lt temples
    • jaw claudication
  • Ex
    • ↑ ESR 105
  • Tentative Dx
    • GCA (giant cell arteritis)
  • Rx
    • corticosteroid

A 51-year-old woman presented with a severe new-onset headache and tenderness over her left temples, jaw claudication, and fever. Laboratory tests revealed an elevated erythrocyte sedimentation rate (105 mm/h). These findings fulfilled the giant cell arteritis (GCA) classification criteria.1 The headache rapidly subsided following corticosteroid therapy.

  • Ex
    • MR
      • diffuse enhancement of Lt pterygoid & temporalis muscle
    • 18F-FDG PET
      • uptake
  • Dx
    • pterygoid myositis

Imaging studies were performed to clarify the etiology since Gram-positive cocci were identified and multiple nodules were revealed by chest X-ray. The brain MRI showed a diffuse enhancement of the left lateral pterygoid and temporalis muscle and fluorine-18-fluorodeoxyglucose PET revealed an intense uptake at the same area (figure). Pterygoid myositis is an underrecognized disease and must be considered as a differential diagnosis of GCA.2

Figure

Brain MRI and 18F-FDG PET
(A) Brain MRI. Fluid-attenuated inversion recovery image shows high signal intensities in the left lateral pterygoid muscle (arrow) and contrast-enhanced T1-weighted image reveals diffuse enhancement of the muscle (arrow).
(B) 18F-FDG PET shows an intense uptake by the left pterygoid muscle (arrow).

Figure

References

  1. Hunder GG, Bloch DA, Michel BA, et al. The American College of Rheumatology 1990 criteria for the classification of giant cell arteritis. Arthritis Rheum 1990;33:1122–1128.
  2. Rahman W, Rahman FZ. Giant cell (temporal) arteritis: an overview and update. Surv Ophthalmol 2005;50:415–428.