Spinal subependymoma

Spinal subependymomas are very rare low-grade tumors (WHO I) of the spinal cord. Like intracranial subependymomas, that are far more common,  spinal subependymomas are slow-growing, discrete tumors with little if any contrast enhancement.

Epidemiology

Due to the small number of cases reported it is difficult to draw firm epidemiological conclusions. These tumors have been reported in a wide age range (6 to 73 years) without a consistent gender predilection ^1,2. 

Clinical presentation

As these tumors are slow-growing, there is usually a fairly lengthy clinical history typically including sensory symptoms, pain, and weakness ². Spinal subependymomas are most often located within the cervical cord, followed by the thoracic cord ^1,2. 

Radiographic features

MRI

Spinal ependymomas present as intramedullary spinal cord tumors with the following features: 

• excentric subpial growth (sometimes extensive) ¹
• expansion of the affected cord over a short distance: bamboo leaf sign ¹
• adjacent syrinx is sometimes present ²

They have similar signal intensity characteristics as intracranial subependymomas ²: 

• T1: isointense to cord
• T2: hyperintense to cord
• T1 C+: variable, ranging from nil to prominent

Treatment and prognosis

Treatment, if clinically indicated, is surgical although as these are indolent and slow-growing complete resection is not necessarily required ². 

Differential diagnosis

Other intramedullary spinal cord tumors are all considerations, however, as spinal subependymomas tend to be intramedullary and only relatively well-circumscribed, the main differential to be considered are:

1. spinal ependymoma: hemosiderin capping is a helpful feature if present
2. spinal astrocytoma

It is difficult to categorically make a preoperative distinction, especially as subependymomas are so much less common than either spinal ependymomas or astrocytomas, however, the absence of significant enhancement, the excentric subpial intramedullary location may serve as clues ¹.