Central neurocytomas are WHO grade II neuroepithelial intraventricular tumors with fairly characteristic imaging features, appearing as heterogeneous masses of variable size and enhancement within the lateral ventricle, typically attached to the septum pellucidum. They are typically seen in young patients and generally have a good prognosis provided a complete resection can be achieved.
Extraventricular neurocytomas (previously known as cerebral neurocytomas) are distinctly uncommon and discussed in a separate article.
Central neurocytomas are typically seen in young patients (70% diagnosed between 20 and 40 years of age) and account for less than 1% (0.25-0.5%) of intracranial tumors 10,11. There is no reported gender predilection 10.
Typically, central neurocytomas present with symptoms of increased intracranial pressure, headaches being most frequent, or seizures (especially tumors with extraventricular extension).
A relatively short clinical course, typically only a few months, is most common. Rarely central neurocytomas may be associated with sudden death secondary to acute ventricular obstruction 4. Also rare, is a sudden presentation due to intraventricular hemorrhage 7.
Central neurocytomas demonstrate neuronal differentiation and histologically appear similar to oligodendrogliomas which, historically, resulted in many tumors erroneously categorized.
The initial description classified them as WHO grade I lesions. However, this was upgraded in 1993 to WHO grade II (and remains so in the 2016 version) as it was recognized that at least some of these tumors exhibited more aggressive behavior 10.
The vast majority of central neurocytomas are located entirely within the ventricles. Typical locations include 4:
- lateral ventricles around foramen of Monro (most common): 50%
- both lateral and 3rd ventricles: 15%
- bilateral: 15%
- 3rd ventricle in isolation: 5%
Central neurocytomas are usually friable grey-colored tumors, sometimes demonstrating areas of calcification and hemorrhage 11.
The cells are typically uniform and round with a salt and pepper finely speckled chromatin 11. They also demonstrate areas of variable architecture that are reminiscent of other tumors, including oligodendrogliomas, pineocytomas and neuroendocrine tumors 11.
Immunohistochemistry confirms the purely neuronal origin by positivity to neuronal markers such as 11:
- synaptophysin: positive
- NeuN: positive
- neuron-specific enolase: positive
- MAP2: usually positive
- class III beta-tubulin: usually positive
Extraventricular neurocytomas are histologically similar but lack an intraventricular component 11.
Ganglioneurocytoma is a variant, usually of extraventricular neurocytomas, demonstrating a distinct ganglion cells component 6,11,12.
Central neurocytomas are usually hyperattenuating compared to white matter. Calcification is seen in over half of cases, usually punctate in nature 4,10. Cystic regions are frequently present, especially in larger tumors. Contrast enhancement is usually mild to moderate. Accompanying ventricular dilatation often present.
- isointense to grey matter
- mild-moderate heterogeneous enhancement
- typically iso to somewhat hyperintense compared to brain
- numerous cystic areas (bubbly appearance), many of which completely attenuate on FLAIR
- prominent flow voids may be seen 10
- calcification is common, typically punctate
- hemorrhage (especially in larger tumors) is common
- uncommonly results in ventricular hemorrhage
- diffusion restriction of the solid component 13
- may have a strong choline peak 13
- glycine peak (3.55ppm) has also been reported 10
A tumor blush is frequently identified, with the mass supplied by choroidal vessels. No large feeding arteries are usually seen.
Treatment and prognosis
Complete surgical resection is usually curative (5 years survival 81%). When only incomplete resection possible or extraventricular extension is present, then adjuvant radiotherapy (and sometimes chemotherapy) are added, although their benefit is not well established.
Cases of CSF dissemination have been reported, but are rare 10.
- more frequent in childhood
- more commonly in 4th ventricle
- supratentorial tumors (esp in children) often have a significant extraventricular (parenchymal) component 4
- homogeneous contrast enhancement
- well circumscribed mass
- typically found in the 4th ventricle
- usually older individuals 8
- may have ependymoma components and look very similar 9
subependymal giant cell astrocytoma
- in patients with tuberous sclerosis
- vivid contrast enhancement
choroid plexus papilloma
- mainly in children
- typically show intense contrast enhancement
- older patients
- usually stronger contrast enhancement
- history of primary (e.g. renal cell carcinoma)
- thalamic glioblastoma
- older patients
- surrounding vasogenic edema
- less lace-like appearance (if any)
- elevated MR perfusion (rCBV)
- this is especially difficult in cases where there is a parenchymal component as histologically the tumors are very similar
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