Clinical significance of a solitary hot spot in the skull

Retrospective evaluation of bone scintigrams over the last 10 years was per formed to determine the incidence of a solitary hot spot in the skull, exam ine its significance in patients with and without extraskeletal malignancy, and determine if location along the suture lines is clinically significant or not. Review of the reports of bone scintigrams in 9968 patients yielded 37 (0.37%) patients with a solitary hot spot in the skull. In the group of 27 patients with extra-skeletal malignancy, the hot spot was secondary to metastasis in four patients and of a non-metastatic origin in 15. In the re maining eight patients, the cause was indeterminate. Two of the four metast atic foci were located along the suture lines. In another group of 10 patie nts without extra-skeletal malignancy, the cause was non-metastatic in eigh t patients and indeterminate in two. No significant differences between the scintigraphic features (intensity of uptake, location and relationship wit h sutures) of metastatic and non-metastatic foci were noted. We conclude th at a solitary hot spot in the skull is rare and is predominantly benign in nature. However, in patients with known extra-skeletal malignancy, approxim ately 21% are secondary to a solitary bone metastasis of the skull. Locatio n of a hot spot along the suture lines may not always be a normal variation and can represent a solitary bone metastasis. ((C) 1999 Lippincott William s & Wilkins).