Spinal subdural hematoma

Last revised by Joshua Yap on 2 Jun 2023

Spinal subdural hematomas (SSDH) are much less common than epidural hematomas; however, progression of symptoms due to compression tends to be faster 1.

Spinal subdural hematomas are a rare entity, much more so than epidural hematomas. In a meta-analysis of over 600 spinal hematomas, only 4% were subdural 2.

Symptoms are those of spinal cord compression or cauda equina syndrome, often presenting initially as back pain and/or radicular pain. Symptoms tend to develop more rapidly with subdural hematomas.

Factors that predispose to subdural hematoma include:

  • coagulopathy

  • anticoagulant therapy 3,4

  • spinal vascular malformations

  • percutaneous spinal intervention 5

  • back surgery 6,7

  • trauma 8: uncommon cause

  • a combination of any of the above

Subdural hematomas occur within the dural sac; therefore, in contradistinction to epidural hematomas, the epidural fat is preserved and the dura is not displaced inward. The hematoma is bounded by the paired lateral denticulate ligaments and the dorsal septum, forming the inverted Mercedes-Benz sign on axial images 1. As such, it compresses the nerve roots but does not extend into the neural foramina or make direct contact with bone. Naturally, smaller collections will not expand the potential subdural space and will, therefore, not create the inverted Mercedes-Benz sign.

CT is the workhorse of emergency medicine and is usually utilized before MRI for emergencies. However, spinal hematomas can easily be missed in the acute setting, especially if it is small. After having identified a subdural hematoma on MRI, it is good practice to revisit the CT study and use a narrow window in an attempt to identify the hematoma. Moreover, revisiting the CT study can sometimes help clarify the diagnosis 1.

A crescentic hyperdense collection may be seen adhering to the inner margin of the dura, separated from the hypodense epidural fat.

MRI is the imaging modality of choice for identifying and characterizing subdural hematomas.

Signal characteristics will vary, depending on the age of the blood.

After having confirmed the location of the collection as subdural on axial images, sagittal images can be utilized for measuring its extent. 

Conservative treatment with watchful waiting (i.e. follow-up with serial MRIs) is acceptable for small collections. In case of significant neurologic defects, laminectomy with clot evacuation is done.

Cervical and thoracic SSDH are associated with a worse outcome than lumbar SSDH, as is coexisting spinal subarachnoid hematoma (SSAH).

It is important to distinguish between subdural hematomas and other entities which can occupy the spinal subdural space:

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Cases and figures

  • Case 1
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  • Case 2
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