What causes intracranial hypotension, particularly in patients with a history of trauma, surgery, lumbar puncture, or connective tissue disorders such as Marfan syndrome or Ehlers-Danlos syndrome?

Causes of Intracranial Hypotension

Intracranial hypotension is caused by cerebrospinal fluid (CSF) leakage through three primary mechanisms: dural tears/defects, leaking meningeal diverticula, and CSF-venous fistulas, with the spine representing the anatomical source in most symptomatic cases. 1

Primary Mechanisms of CSF Loss

The three main pathophysiologic causes are:

• Dural tears or defects that allow CSF to leak from the thecal sac into the epidural space 1
• Leaking meningeal diverticula (outpouchings of the dura that develop weak points) 1
• CSF-venous fistulas where abnormal connections form between the CSF space and venous system 1

The spine, particularly the lower cervical and upper thoracic regions, is the predilection site for CSF leaks because intracranial hydrostatic pressure is slightly negative in the upright position while spinal pressure remains positive, creating a pressure gradient that drives leakage 1, 2

Classification: Spontaneous vs. Secondary

Spontaneous Intracranial Hypotension (SIH)

Spontaneous cases occur without an obvious precipitating event and have an estimated incidence of 3.7-5 per 100,000 annually (though likely underdiagnosed). 1

Risk factors for spontaneous CSF leaks include:

• Connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome) that weaken dural integrity 1, 2
• Spinal osteophytes that can perforate the dura through mechanical stress 1, 2
• Weakened or ectatic dura and meningeal cysts associated with collagen vascular disease 1, 2
• History of bariatric surgery where rapid loss of epidural fat may weaken dural support 1
• Mechanical stress on the spine, particularly in the cervicothoracic junction 2

Secondary Intracranial Hypotension

Secondary causes result from identifiable precipitating events:

• Lumbar puncture (post-dural puncture headache occurs in 2-8% of cases, with risk related to needle type and gauge) 1, 3, 2
• Spine surgery or neurosurgical procedures with accidental or intentional dural opening 3, 2
• Trauma to the spine causing dural disruption 1, 3, 2
• Epidural anesthesia with unintended dural puncture 3, 4
• Chiropractic manipulation (rare iatrogenic cause) 2
• Excessive surgical CSF drainage from shunts or external ventricular drains 3

Rare and Emerging Causes

• Degenerative spine disorders including spinal canal stenosis can increase intradural pressure, potentially causing dural tears and subsequent CSF leakage 2, 5
• Spinal canal stenosis may create a blockage that increases pressure cranially, leading to dural rupture at vulnerable sites 5

Important Clinical Pitfalls

The true incidence of intracranial hypotension is likely higher than reported because it remains highly underdiagnosed and frequently misdiagnosed. 1 Common errors include:

• Failing to consider intracranial hypotension in patients with orthostatic headache who lack a clear history of dural puncture 1
• Missing the diagnosis in patients with atypical presentations (coma, frontotemporal dementia-like symptoms, neck pain, or radicular symptoms rather than classic orthostatic headache) 3, 2
• Not recognizing that approximately 20% of patients with SIH have normal brain MRI findings despite active CSF leak 1