Subependymal hamartoma

Subependymal hamartomas are seen in patients with tuberous sclerosis. They are located along the ventricles and are mostly asymptomatic. As with other hamartomas, they grow at the same rate as the surrounding tissues.

On imaging, they appear as small intraventricular masses, smaller than 1 cm, and demonstrate variable signal on MRI with contrast enhancement, and may calcify.

Epidemiology

Subependymal hamartomas are a well-known manifestation of tuberous sclerosis, affecting 80% of patients with the condition ¹. They are visible within the first six months of age ².

Clinical presentation

Subependymal hamartomas are often asymptomatic. When symptoms occur, they are usually a result of obstructive hydrocephalus from the mass effect to the ventricular system.

Radiographic features

Subependymal hamartomas are small irregular nodules, measuring <1 cm, with their long axis perpendicular to the ventricular surface. They grow in proportion to the surrounding tissues and may calcify with increasing age.

CT

• appear as small irregular intraventricular mass.
• smaller than 1 cm
• calcification is common (88%)
• accompanying hydrocephalus may be present
• variable contrast enhancement

MRI

• T1: variable signal, frequently hyperintense to grey matter 
• T2: variable signal, frequently iso to hyperintense to grey matter
• T1 C+ (Gd): also shows variable enhancement
• Marked hypointense areas are in keeping with calcification

Treatment and prognosis

Subependymal hamartomas are mostly asymptomatic. However, they may progress to subependymal giant cell astrocytoma which may lead to obstructive hydrocephalus, causing morbidity or mortality. Therefore, surveillance is offered to patients with tuberous sclerosis.

Should these tumours become symptomatic or large, surgical treatment is required.

Differential diagnosis

• subependymal giant cell astrocytoma 
  • larger than 1 cm
  • increases in size in serial imaging ^3,4
• subependymal grey matter heterotopia
  • smooth and ovoid
  • long axis parallel to the ventricular surface
  • follows grey matter signal
• ring-shaped lateral ventricular nodules ⁵
  • smaller than 1 cm
  • ring-shaped with a core signal that follows CSF signal intensity
  • does not increase in size on follow-up