The hot skull sign on bone scans of obese patients resulting from disparate soft tissue attenuation.

We have frequently observed diffusely increased skull activity on bone scans of obese patients, who do not have evidence of metabolic or metastatic bone disease. Skull activity of 25 obese patients were compared to that of age and sex-matched nonobese 25 patients visually and quantitatively. The results clearly indicated that diffusely increased skull activity is significantly more common on bone scans of obese patients because of disparate attenuation of overlying soft tissues. This knowledge will help obviate the need for additional radiologic and/or laboratory tests in search of other conditions associated with hot skull, ie, Paget's disease and metabolic bone disorders such as renal osteodystrophy and primary hyperparathyroidism.