In an adult without a history of trauma who presents with orthostatic headache, eye pain, and pulsatile tinnitus, what is the most likely diagnosis?

Spontaneous Intracranial Hypotension (SIH)

The most likely diagnosis in a patient presenting with postural headache, eye pain, and pulsatile tinnitus is spontaneous intracranial hypotension (SIH) caused by cerebrospinal fluid (CSF) leakage from a spinal source. 1, 2

Key Diagnostic Features

This clinical triad strongly suggests SIH because:

• Postural/orthostatic headache is the pathognomonic feature of SIH, defined as headache that is absent or mild (1-3/10) upon waking, develops within 2 hours of becoming upright, and improves by >50% within 2 hours of lying flat 1, 3
• Eye pain (visual disturbances) is a common accompanying feature of SIH due to downward traction on cranial nerves and brain structures 3, 4
• Pulsatile tinnitus is a key associated symptom that increases diagnostic certainty for SIH and represents a predictor of recurrence 1, 2, 3

Pathophysiology

The mechanism involves CSF leakage through three primary routes:

• Dural tears or defects allowing CSF to leak from the thecal sac into the epidural space 2, 5
• Leaking meningeal diverticula (weak points in dural outpouchings) 2, 5
• CSF-venous fistulas (abnormal connections between CSF space and venous system) 2, 5

The spine is the anatomical source in most symptomatic cases because positive hydrostatic pressure exists in the spine relative to atmosphere, while intracranial pressure is slightly negative in the upright position 2, 5

Critical Differential Diagnoses to Exclude

Before confirming SIH, you must exclude:

• Postural Orthostatic Tachycardia Syndrome (PoTS): Perform formal standing test documenting heart rate increase >30 beats per minute; note that a negative test does not exclude PoTS if clinical suspicion remains high 1, 3
• Orthostatic hypotension: Document blood pressure drop >20 mmHg systolic and/or >10 mmHg diastolic on standing 3
• Cervicogenic headache: Distinguished by headache provoked by cervical movement (not posture), reduced cervical range of motion, and myofascial tenderness 1, 3
• Migraine: Distinguished by headache provoked by movement (not posture), migrainous biology including aura, and vertigo rather than hearing impairment and tinnitus 1, 3

Immediate Diagnostic Workup

Order two complementary imaging studies immediately:

1. MRI brain with IV contrast to confirm intracranial hypotension features including diffuse pachymeningeal enhancement, venous sinus engorgement, midbrain descent, pituitary enlargement, and ventricular collapse 1, 2, 3
2. MRI complete spine with fluid-sensitive sequences to localize the spinal CSF leak source via epidural fluid collections, dilated epidural venous plexus, or CSF-venous fistula 1, 2, 3

Critical Diagnostic Pitfall

Do not exclude SIH based on normal CSF opening pressure. CSF pressure can be normal in patients with SIH because the underlying mechanism is CSF volume insufficiency (hypovolemia) rather than pressure 1, 2, 6. Clinical presentation and imaging findings are more important than measured CSF pressure 2

Additionally, approximately 20% of patients with active CSF leak have normal brain MRI findings, so negative initial imaging does not exclude the diagnosis if clinical suspicion remains high 5

Predisposing Conditions to Consider

Inquire about:

• Connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome) and joint hypermobility disorders that weaken dural integrity 1, 5
• History of bariatric surgery where rapid loss of epidural fat may weaken dural support 2, 5
• Spinal pathology including osteophytes, disc herniation, and discogenic microspurs 1, 2

Treatment Approach

Early epidural blood patch (EBP) is first-line treatment and should be performed as soon as possible after diagnosis to shorten disease duration and minimize risk of complications 2, 3, 6. Non-targeted EBP is appropriate initially, with myelography reserved for cases that fail to respond or have persistent symptoms 2

Life-Threatening Complications to Monitor

Cerebral venous thrombosis (CVT) occurs in approximately 2% of SIH cases and can be diagnosed with CT or MR venography 2. Other serious complications include subdural hematomas and altered mental status requiring urgent intervention 4, 6