Intracranial hypotension - subdural hematoma

Case contributed by Eid Kakish
Diagnosis certain

Presentation

Ongoing postural headache which, described by the patient, became more progressive and constant over the past few months. Patient is on prophylactic low-dose antiplatelets. No history of head trauma.

Patient Data

Age: 75 years
Gender: Male

Initial MRI

mri

This is the patient's initial unenhanced brain MRI, revealing a right hyperacute frontoparietal subdural hematoma with no significant mass effect or midline shift. 

Changes of white matter microvascular disease in the form of T2 and FLAIR hyperintensities in the periventricular white matter of both cerebral hemispheres. 

Age-related involutional changes in the form of cortical volume loss and prominence of extra-axial CSF spaces and ventricular system.

Follow-up MRI

mri

A follow-up contrast-enhanced MRI revealed increase in thickness of the previous right frontoparietal subdural hematoma, with mild mass effect manifested by effacement of the adjacent sulci, particularly in the right parietal lobe. 

Uniform diffuse pachymeningeal thickening and enhancement, associated with distension of the dural venous sinuses and minimal downward displacement of the splenium of the corpus callosum "droopy penis sign". 

The brainstem is unremarkable. No tonsillar ectopia. 

Old CT abdomen/pelvis

ct

In retrospect, an old CT abdomen/pelvis was reviewed. 

Severe degenerative changes at L4-L5 and L5-S1, manifested by marked intervertebral disc space narrowing and vacuum phenomena. A few tiny intradural gas locules are also evident, possibly suggesting a degenerative dural tear at this level, which may likely be the source of CSF leak. 

Case Discussion

The presence of an obvious subdural hematoma (SDH) on the initial scan was a plausible explanation for patient's worsening headaches (Satisfaction of search error). 

The diffuse pachymeningeal thickening was initially seen on the FLAIR sequence of the subsequent scan, before contrast administration. However, it was clearly present, but to a lesser degree, on patient's initial unenhanced brain MRI. These findings were probably accentuated by the cortical involutional changes and prominence of the CSF spaces. 

In Intracranial hypotension (ICH), the most common MRI finding is thickening and enhancement of the pachymeningeal coverings. According to the Monro-Kellie hypothesis, a decrease in one of the three major intracranial components (brain, CSF, blood) will result in a compensatory increase in the others, to maintain dynamic equilibrium. This theory explains the secondary vascular distension encountered in ICH, accounting for Pachymeningeal enhancement and subdural fluid collections. 

Subdural hematoma formation in patients with ICH is possibly secondary to shearing of the bridging cortical veins as a consequence of CSF volume reduction. The age-related cortical changes in our patient might have accentuated this process. 

Other classical signs of ICH include sagging of the brainstem, acquired tonsillar ectopia, diffuse cerebral edema and pituitary gland enlargement, in addition to other quantitative signs (Mamillopontine distancePontomesencephalic angleInterpeduncular angle). Most of these signs are not clearly depicted in this patient. A possible explanation for this is the presence and subsequent enlargement of a SDH, which might have achieved intracranial equilibrium, correcting the abnormally low intracranial pressure by replacing the lost CSF volume by subdural blood.

The presence of tiny intradural gas locules on the previous CT raised the possibility of a tiny underlying degenerative dural tear at L5/S1. However, further imaging investigations such as a lumbar MRI/ CT myelography are needed to confirm this suspicion.

It was decided that this patient would likely benefit from a speculative lumbar Epidural blood patch with follow-up imaging. 

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