A 75-year-old man with a known history of prostate adenocarcinoma presented with progressive worsening headache and retro-ocular pain.
A 75-year-old man with a known history of prostate carcinoma presented with worsening headache and retro-ocular pain on both sides. Neurological examination was unremarkable. No cranial nerve deficit was detected. Routine blood investigations were within normal limits except for an elevated PSA levels (prostate specific antigen). Magnetic resonance imaging revealed diffuse pachymeningeal thickening along the cerebral convexities which demonstrated avid enhancement on post contrast scan. Relatively flat dural based masses were seen along the basilar pachymeninges along the floor of middle cranial fossa. No evidence of abnormal leptomeningeal enhancement was seen. There was no concomitant brain parenchymal lesion present. Fat suppressed T2-weighted MR images revealed osseous lesions involving the bilateral greater sphenoid wings with associated soft tissue component. There was an associated extraconal mass seen extending into the right orbit. These imaging findings, in a known case of prostate adenocarcinoma, suggested dural and calvarial metastases which was confirmed on histopathology.
Dural metastasis accounts for 9% of all central nervous system metastases. A range of malignant neoplasms can secondarily involve the pachymeninges such as breast carcinoma, prostate carcinoma, melanoma, secondary CNS lymphoma and leukaemia. Intracranial metastases are an uncommon occurrence in prostate carcinoma. We present a 75-year-old male patient, a known case of prostatic adenocarcinoma, who presented for MR imaging following worsening headache and retro-ocular pain.
As mentioned, intracranial metastases are rare in prostate carcinoma and occur quite late in the course of the disease. It usually signifies extensive systemic dissemination and an end-stage disease. Central nervous dissemination of the prostatic malignancy is thought to be either through direct extension from calvarial metastases (57 %) or secondary to haematogenous spread (43 %). Haematogenous spread may be secondary to arterial dissemination of malignant cells or through retrograde seeding via Batson’s valveless vertebral venous plexus. These patients often have concomitant secondaries in the bones and/ or lungs and thus have a poor prognosis. Uncommonly, the patient presents with neurological symptoms as the first manifestation of the disease. Pachymeninges (dura-arachnoid) are the preferred site of intracranial prostatic metastases followed by cerebral parenchymal and cerebellar deposits. Dural metastases can have a diverse appearance ranging from multiple nodular lesions to diffuse smooth dural thickening. This is in contrast to the normal thin, linear and discontinuous enhancement of the normal dura mater. Rarely a solitary lobulated dural based mass may be seen extending into epidural and subdural spaces. Non-traumatic spontaneous subdural haematomas secondary to prostatic dural metastases have also been described in the literature. Similar imaging findings of diffuse pachymeningeal thickening and enhancement may be encountered in various benign and malignant lesions such as: Post-operative dural thickening, intracranial hypotension, granulomatous diseases such as sarcoidosis and Wegener's granulomatosis, infective pathologies (tuberculous, fungal and syphilis), primary dural based neoplasm (meningioma, reactive), metastatic disease (breast carcinoma, melanoma and lymphoma). Although it may be challenging to differentiate these entities purely based on the imaging findings, there are few findings which may aid in narrowing down the differentials. Granulomatous meningitis preferentially involves the basilar pachymeninges and not the cerebral convexities. Pachymeningeal metastases can be associated with abnormal leptomeningeal enhancement too, as is often seen with carcinoma breast metastases, melanoma metastases and secondary CNS lymphoma. Dural based masses such as en-plaque meningiomas typically demonstrate disproportionate osseous hypertrophy and/or osseous invasion with or without the presence of dural tail sign. Dural thickening and enhancement in intracranial hypotension is often associated with enlargement of the pituitary gland, descent of the brain and subdural effusions or haemorrhage.
To conclude, pachymeningeal thickening and enhancement has a wide list of differentials. In an elderly male, the diagnostic possibility of dural metastases from a prostatic carcinoma should be considered which can manifest as smooth or nodular pachymeningeal thickening or multiple dural based masses on MR imaging.
Differential Diagnosis List
Dural metastases from prostate carcinoma.
Dural metastases from prostate carcinoma.