Unenhanced head CT
A 69-year-old man suffering from multiple cervical spine fractures following low-energetic trauma was diagnosed with diffuse osteoblastic metastases in the entire axial skeleton. Clinical work-up revealed advanced prostate cancer. For staging purposes and because of headache and altered mental status, brain CT and brain MRI were performed.
An initial unenhanced brain CT was performed because of the patient’s poor renal function. This revealed subcortical oedema in the parietal and temporal lobe on the right side, with secondary mass-effect on the right lateral ventricle. Another finding was marked right parietal and parafalcine dural thickening.
Subsequent MRI of the brain after IV gadolinium administration confirmed an enhancing right temporal, parietal and occipital dural thickening, extending to the right side of the falx. No broad dural base could be seen. There was vasogenic oedema in the right temporal lobe. Both CT and MRI also showed diffuse osteoblastic lesions in the skull.
Prostate cancer represents the fifth leading cause of cancer mortality in men and is the third most diagnosed form of cancer in male patients. The most important risk factors for developing this disease are age, family history of prostate cancer, black race and genetic factors . The prognosis of prostate cancer is in large parts dependent on the presence of lymph node involvement as well as distant metastases. The most common sites of lymphatic metastases are the paraaortic and pelvic lymph nodes. Haematogeneous disease spread mainly occurs in bones (90%). Other relatively frequent sites of tumour spread are lungs (46%) and liver (25%) .
Intracranial spread of prostate cancer is rather uncommon with dural involvement accounting for only 0.04% according to a single institution study. In autopsy studies, this number increases to 5.9 % [2, 3]. However, prostate cancer is the second most common cancer form, after breast cancer, to have dural dissemination .
Patients with dural metastases usually present with headache and cranial nerve palsy. Other possible symptoms are visual disturbances, alterations in mental state and seizures [4, 5].
Two routes of tumour spread have been proposed. One is a direct spread through retrograde flow in the valveless vertebral venous plexus of Batson. Batson was able to illustrate this in cadaver experiments after administrating contrast in the prostatic veins. A possible different route is based upon the cascade theory. This theory proposes that metastases spread from bone to adjacent structures, and is usually accepted in patients with extensive metastases to the calvarium [6, 7, 8].
Dural metastases primarily appear as solitary or multifocal areas of dural thickening, which may be nodular. Since there is no blood-brain barrier at this level, the lesions show intense homogeneous enhancement after administration of IV-contrast. Adjacent bony erosions and metastases in the skull may help to differentiate dural metastases from meningioma. Rapid lesion growth on subsequent scans also favours metastases. In rare cases, dural metastases may cause subdural haematoma [4, 5].
Patients with advanced prostate cancer and dural metastases generally have a poor prognosis with an estimated mean survival of 3 to 4 months .
Written informed patient consent for publication has been obtained.
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