Subependymoma was first discovered by Ilya Mark Scheinker, a Russian physician, in 1945.^[1]

There is no established system for the classification of subependymoma.

Subependymoma arises from subependymal glial cells, although it can also arise from astrocytes from the subependymal plate, ependymal cells, and mixed ependymal and astrocytic cells.^[2][3]

Subependymoma is most commonly seen in the fourth ventricle, but it can arise anywhere where there is ependyma. The distribution in the ventricular system is as follows:^[4][3]

• Fourth ventricle: 50 – 60%
• Lateral ventricles (usually frontal horns): 30 – 40%
• Third ventricle: rare
• Central canal of the spinal cord: rare

• On gross pathology, subependymoma is characterized by a small, white to grey, firm, well circumscribed, solid, avascular mass attached to the ventricular wall by a narrow pedicle.^[2][3]

On microscopic histopathological analysis, subependymoma is characterized by the following features:^[4]

• Microcystic spaces and bland appearing cells without appreciable nuclear atypia or mitoses.
• The nuclei tend to form clusters.
• No high grade features (mitoses, Ki-67 / MIBI index > 1.5%, necrosis) are present.
• Loose pseudorosettes are observed.

Subependymoma is characterized by positive tumor marker GFAP. Mixed populations of cells may be variably positive for:^[4][5]

• Olig2
• NHERF1
• Sox2
• CD44

The cause of the development of subependymoma has not been identified.

Subependymoma must be differentiated from:^[6][3]

• Neoplasms of the ventri­cular wall and septum pellucidum
  • Ependymoma
  • Central neurocytoma
  • Subependymal giant cell astrocytoma
• Neoplasms of the choroid plexus
  • Choroid plexus papilloma and carcinoma
• Others
  • Intraventricular meningioma
  • Intraventricular metastasis
  • Oligodendroglioma
  • Pilocytic astrocytoma
  • Glioblastoma multiforme
  • Medulloblastoma
  • Intraventricular teratoma

• The frequency of asymptomatic subependymomas was 0.4% in 1,000 serial routine necropsies and 0.7% in symptomatic subependymomas from 1,000 serial surgical specimens of intracranial neoplasms.^[7]
• The incidence of subependymoma was estimated to be 0.7 cases per 100,000 individuals with pathologically proven intracranial neoplasms.^[8]

• Patients of all age groups may develop subependymoma.

• Subependymoma is a rare disease that tends to affect middle-aged adults and the elderly population (typically in the 5th to 6th decades).^[9]

• Males are more commonly affected with subependymoma than females.
• The male to female ratio is approximately 2.3 to 1.^[9]

The risk factors in the development of subependymoma are not well defined.

• If left untreated, patients with subependymoma may progress to develop seizures and obstructive hydrocephalus.^[10]
• Subependymoma is a slow-growing tumor with an indolent course.^[11][5]

• Obstructive hydrocephalus is a common complication of subependymoma.^[10]

• The prognosis of subependymoma is excellent with complete excision of the tumor.^[2][12]
• Common complications of subependymoma are hydrocephalus and focal neurological deficits due to mass effect.^[3]

• Typically patients of subependymoma are asymptomatic and small lesions are discovered incidentally.
• Symptoms of subependymoma include:^[13][14][3]
  • Symptoms due to elevated intracranial pressure
    • Headache
    • Nausea
    • Vomiting
  • Neurological symptoms
    • Seizures
    • Sudden loss of awareness
    • Transient loss of memory

• Patients with subependymoma usually appear normal.
• Physical examination may be remarkable for:^{[15][16][17][18][3][19]}

• Abnormal pupillary reflex
• Visual field defects
• Gait changes
• Bilateral Babinski sign
• Depressed Glasgow coma score (GCS)
• Decreased muscle strength
• Decreased deep tendon reflexes
• Sensation defects
• Hearing problems and abnormal Rinne and Weber tests

There are no specific laboratory findings associated with subependymoma.

There are no ECG findings associated with subependymoma.

There are no x-ray findings associated with subependymoma.

There are no echocardiography/ultrasound findings associated with sybependymoma.

Head CT scan is helpful in the diagnosis of subependymoma. On CT scan, subependymoma is characterized by:^[20]

• Iso- and hypodense intraventricular mass
• Positive mass effect
• No enhancement
• If large, it may have cystic or even calcific components
• No vasogenic edema

Brain MRI is helpful in the diagnosis of subependymoma. On MRI, subependymoma is characterized by:

There are no other imaging findings associated with subependymoma.

There are no other diagnostic studies associated with subependymoma.

There is no medical therapy available for the treatment of subependymoma.

Surgery is the mainstay of therapy for subependymoma. Incidental intraventricular subependymoma can be managed conservatively through MRI surveillance. Surgical resection is indicated for:^[3][21][22]

• Symptomatic tumors
• Tumors without a clear imaging diagnosis

There are no established measures for the secondary prevention of subependymoma.

There are no established measures for the primary prevention of subependymoma.