Clinical History
A 65-year-old male outpatient was referred for a cranial MRI. He complained of occasional dizziness and disturbances of equilibrium. Headaches were denied. Personal and family histories were uneventful. After the initial imaging studies, the patient refused treatment and re-appeared 21 months later in a much worse condition.
Imaging Findings
The first MRI showed a small lesion in the left frontal septum pellucidum (SP), slightly protruding into the adjacent lateral ventricle (Fig. 1a, b). The lesion appeared heterogeneously hyperintense on T2-, and isointense on T1-weighted images. After Gadolinium, it enhanced moderately. A native cranial CT was performed the next day to look for calcifications (Fig. 1c). The case was presented to a board of clinical neuroscience experts, who recommended surgical excision. Regrettably, the patient refused an operation, and completely defied any further treatment.
His health status deteriorating rapidly, he returned 21 months later, complaining of severe headaches, nausea and vomiting. On a new cMRI study (Fig. 2), the tumour had grown into a large mass, which crossed the midline and presented with bilateral intraventricular seeding. MRI findings at that time strongly suggested glioblastoma. The patient finally consented to an operation and glioblastoma multiforme was confirmed by biopsy. The patient deceased shortly thereafter.
Discussion
The septum pellucidum (SP) forms the inner wall of the lateral ventricles. It is a rather uncommon site for a primary brain tumour. Lesions confined to this region normally do not cause any specific neurological symptoms, so newly diagnosed tumours of the SP used to be very advanced before cross-sectional imaging became available. The right diagnosis often was not made until symptoms from elevated intracranial pressure had developed. Until 1981, the most common neoplasms found in the SP were of gliomatous origin [1]. However, due to incidental detection by MRI or CT, numerous case reports have appeared since then, dealing with a broad spectrum of neoplastic and non-neoplastic lesions of the SP. According to those reports, the most common benign neoplasms arising from the SP seem to be central neurocytoma [2] and subependymoma [2, 3]. Other more than sporadic neoplasms of the SP are mentioned in the differential diagnosis list at the end of this text. Since glioblastoma is growing rapidly, it is typically detected at an advanced stage. There are no literature reports on its early occurrence in the SP. Non-neoplastic midline lesions of the SP, such as cysts or lipomas, are developmental in origin and can be easily differentiated by MRI or CT in the vast majority of cases. However, in solid soft-tissue masses of the SP, MRI is unable to differentiate benign from malignant. PET or MR spectroscopy could have been used in the present case, if the patient had been more compliant. However, even benign tumours of the SP may cause death from obstruction of the CSF circulation or intraventricular bleeding. As a consequence, surgical excision is often the only method to obtain a biological diagnosis and to treat a septum pellucidum mass. Unfortunately, surgical complication rates are high [4].
Differential Diagnosis List
Early glioblastoma of the septum pellucidum
Neurocytoma
Astrocytoma
Oligodendroglioma
Germ cell tumours
Subependymoma
DNET (Dysembryoplastic neuroepithelial tumour)
Final Diagnosis
Early glioblastoma of the septum pellucidum
