99mTc-SPECT in the diagnosis of skull base metastasis.

Abstract

To evaluate the role of bone SPECT in diagnosing metastasis to the skull base in cancer patients. Skull base metastasis often causes characteristic clinical syndromes. Antitumor treatment ameliorates or stabilizes symptoms in most patients. Diagnosis may be difficult when neuroimaging studies are negative (as occurs in about one-quarter of patients). Case reports have suggested a role for bone SPECT in these patients. We reviewed the charts of all patients (1993-1996) at our institution who had skull base SPECT and at least one neuroimaging study (CT or MRI) for clinically suspected metastasis to the base of the skull. Bone SPECT, CT, and MRI were blindly re-evaluated. We studied 56 patients, of whom 36 had skull base metastasis. Twenty patients had other causes of the clinical syndrome, including leptomeningeal and posterior fossa metastasis, or benign causes. In 29 of 36 patients (81%) with skull base metastasis, CT or MRI clearly demonstrated the lesion. Bone SPECT identified a hot spot in the appropriate region of the skull base in 28 of 36 patients (78%). All seven patients with negative CT or MRI had positive SPECT and four of these had a response to anti-tumor treatment. SPECT of the skull base can demonstrate lesions not identifiable by CT or MRI. In cancer patients suspected of having skull base metastasis, we recommend SPECT of the skull base when CT or MRI studies are negative.