Clinical History
A 30-year-old female patient, who had been operated for a supratentorial neoplasm 3 years ago, presented with worsening paraparesis and progressive headache of 1 month duration. She was brought in a delirious state for a contrast enhanced MR evaluation of brain and spine.
Imaging Findings
The patients MR imaging of spine revealed subtle hypointense intradural soft tissue extending throughout the dorsolumbar spine which was most pronounced in the region of cauda equina nerve roots and the conus medullaris. Post contrast fat saturated T1-w images demonstrated diffuse enhancement of the subarachnoid space throughout the spine. Enhancing material was encasing the cord with no CSF visible, giving the appearance of a T2w image (Fig. 1). Post contrast MR imaging of brain revealed diffuse enhancement of the leptomeninges and basal cisterns (peri-mesencephalic and prepontine) with enhancing nodular lesion in the suprasellar cistern (Fig. 2, 3). This appearance has been referred to as "zuckerguss" or sugar icing suggesting leptomeningeal dissemination of the ependymoma. An abnormal ependymal enhancement was also seen along the bilateral lateral ventricles with multiple periventricular enhancing nodular lesions consistent with CSF dissemination of the ependymoma (Fig. 4). Additionally there was continuous pachymeningeal (dural) enhancement noted suggesting possible pachymeningeal infiltration (Fig. 5). Based upon these characteristic imaging findings, in an operated case of supratentorial ependymoma, a diagnosis of extensive cranial and spinal meningeal carcinomatosis was made.
Discussion
The so called "sugar coating" or zuckerguss (German for sugar icing) is seen in the brain and spinal cord in patients with leptomeningeal carcinomatosis and leptomeningeal drop metastases respectively. It is seen on the post contrast CT or MR images as multiple enhancing masses within the subarachnoid space, or diffuse leptomeningeal enhancement along the cerebral or spinal surface which has been likened to cake icing. This leptomeningeal involvement can be sequel of CNS metastases of systemic malignancies as well as from primary central nervous system neoplasms. Primary intracerebral tumours which may show leptomeningeal dissemination include medulloblastoma, primitive neuroectodermal tumour (PNET), ependymoma, germinoma, choroid plexus carcinoma and Glioblastoma multiforme. Or, more commonly, leptomeningeal spread may be subsequent to widespread metastatic spread of breast carcinoma, bronchogenic carcinoma, melanoma, lymphoma and leukaemia. Various postulated modes of leptomeningeal seeding include: (1) haematogenous spread to choroid plexus and subsequently to leptomeninges, (2) primary haematogenous metastases through the leptomeningeal vessels, (3) metastasis via the paraspinal Batson venous plexus, (4) retrograde dissemination along perineural lymphatics and sheaths, (5) direct extension from contiguous tumour deposits. Leptomeninges i.e. the pia and arachnoid enclose the subarachnoid CSF space. Metastasis to the subarachnoid space subsequently spreads widely along the surface of brain and spine due to CSF flow as well as along the ventricular surface. The infiltration is greatest along the basilar cisterns and the cauda equina and dorsal surface of the spinal cord. These patients usually present with multiple cranial nerve deficits and can also present with features of raised intracranial pressure owing to hydrocephalus. Vascular encasement can cause vasculitic or major vascular territory infarcts. At times, patient may present with seizures, focal neurological deficit, ataxia or incontinence. Imaging plays an important role in the clinical work-up of these patients. Post-contrast MR imaging has a higher sensitivity than a contrast enhanced CT scan. T1-weighted post contrast MR images can vividly demonstrate diffuse abnormal enhancement of the basal cisterns and leptomeninges along the cortical sulci. Leptomeningeal seeding may show predilection for regions of relative CSF stasis such as the basal cisterns, cerebellopontine angles and Meckels caves in the brain and the cauda equina nerve roots in the spine. The abnormal leptomeningeal enhancement may manifest as a sheetlike mold along the pial surface or may manifest as multiple nodules of various sizes studding the brain or cord surface or the nerve roots. Abnormal ependymal enhancement or intraventricular enhancing masses can also be seen. Larger intraventricular or cisternal lesions may result in obstructive hydrocephalus, while interference with CSF resorption due to tumour seeding of the arachnoid granulation can lead to non-obstructive hydrocephalus. Post contrast FLAIR images have also proven useful in depicting well the leptomeningeal seeding. The differentials of abnormal leptomeningeal enhancement include tubercular meningitis, fungal meningitis or neurosarcoidosis. However, history of a primary cerebral neoplasm or a known systemic primary neoplasm helps in clinching the diagnosis. Patients with leptomeningeal carcinomatosis carry a poor prognosis with median survival rate of 6 weeks without treatment and 6 months with treatment.
Differential Diagnosis List
Leptomeningeal carcinomatosis in supratentorial ependymoma
Final Diagnosis
Leptomeningeal carcinomatosis in supratentorial ependymoma
