What is the next step in managing an adult patient with a history of headaches, whose headache worsens when laying down, with negative computed tomography (CT) and magnetic resonance imaging (MRI) results?

Headache Worsening When Laying Down with Negative Neuroimaging

Consider spontaneous intracranial hypotension (SIH) as the primary diagnosis and proceed with MRI brain with IV contrast to evaluate for characteristic findings of CSF leak, including diffuse pachymeningeal enhancement, brain sagging, subdural fluid collections, and venous sinus engorgement. 1

Clinical Context and Diagnostic Approach

The presentation of headache worsening when lying down represents an atypical orthostatic pattern that is the opposite of classic orthostatic headaches. This "reverse orthostatic" pattern raises specific diagnostic considerations that standard CT and MRI without contrast may miss 1.

Why Standard Imaging May Be Negative

• Standard non-contrast CT and MRI have limited sensitivity for detecting the subtle findings of intracranial hypotension, particularly early in the disease course or in cases with atypical presentations 1
• The ACR Appropriateness Criteria emphasize that MRI brain with IV contrast is essential for detecting the characteristic pachymeningeal enhancement pattern of SIH 1
• In the case series from Journal of Neurosurgery, initial MRI demonstrated smooth, diffuse dural and leptomeningeal enhancement that was only visible with contrast administration 1

Critical Red Flag: Cerebral Venous Thrombosis Risk

This presentation pattern carries significant risk for cerebral venous thrombosis (CVT), which can be life-threatening and requires urgent diagnosis. 1, 2

• Intracranial hypotension creates a hypercoagulable state through venous stasis and increased blood viscosity from CSF volume loss 1
• CVT can develop as a complication of SIH, presenting with headache that worsens in recumbent position as intracranial pressure rises 1, 2
• MRI brain with contrast plus MR venography is mandatory when headache pattern suggests increased intracranial pressure or when Valsalva maneuvers worsen symptoms 2

Recommended Diagnostic Algorithm

Step 1: Obtain MRI Brain with IV Contrast

• Look for diffuse pachymeningeal enhancement (most sensitive finding for SIH) 1
• Assess for brain sagging (descent of brainstem, flattening of pons) 1
• Evaluate for subdural fluid collections or small subdural hematomas 1
• Check for venous sinus engorgement as compensatory mechanism 1

Step 2: Add MR Venography

• Essential to exclude cerebral venous thrombosis, which can complicate SIH or present independently with similar symptoms 1, 2
• The Headache Consortium identifies headache worsened by positional changes as a feature associated with increased likelihood of significant intracranial pathology 1, 2

Step 3: If Brain Imaging Shows SIH Features, Proceed to Spinal Imaging

• MRI complete spine without and with IV contrast to localize CSF leak source 1
• Look for epidural fluid collections, meningeal diverticula, or ventral dural defects 1
• MR myelography may be added for better visualization of CSF leak site 1

Step 4: If Initial MRI is Negative but Clinical Suspicion Remains High

• Consider dynamic CT myelography or digital subtraction myelography for definitive leak localization 1
• These invasive studies are reserved for cases where treatment (epidural blood patch) is being planned 1

Important Clinical Pitfalls

Pitfall 1: Assuming Negative Standard Imaging Rules Out Pathology

• The Headache Consortium guidelines note that absence of abnormality on standard neuroimaging does not reliably exclude significant pathology when red flag symptoms are present 1
• Headache worsened by positional changes (including lying down) is specifically mentioned as a feature that increases likelihood of abnormality, even with negative initial imaging 1, 3

Pitfall 2: Missing the "Rebound Headache" Phenomenon

• If patient has had recent epidural procedures or lumbar puncture, consider rebound intracranial hypertension following treatment of CSF leak 1
• This presents with headache relief when upright and worsening when recumbent—the exact opposite of typical SIH 1
• Rebound headaches are usually self-limited and managed conservatively with acetazolamide, not repeat imaging 1

Pitfall 3: Delaying Diagnosis of CVT

• CVT can present with altered mental status in only 8% of cases, meaning most patients appear neurologically normal initially 2
• The combination of SIH and CVT is rare but life-threatening, requiring immediate anticoagulation despite presence of subdural collections 1
• In the reported case, CVT developed acutely in a patient with known SIH, progressing to hemorrhagic venous infarction within hours 1

When Neuroimaging Guidelines Don't Apply

The standard Headache Consortium recommendations state that neuroimaging is not usually warranted in patients with normal neurological examination 1. However, these guidelines explicitly acknowledge that:

• Atypical headache features warrant lower threshold for imaging 1
• Headache worsening with positional changes (Valsalva, lying down) is specifically identified as a red flag 1, 3
• The 0.2% yield of imaging in typical migraine with normal exam does not apply to patients with atypical features 4, 5

Treatment Implications

Once SIH is confirmed:

• Conservative management first: bed rest, hydration, caffeine 1
• Epidural blood patch is definitive treatment if conservative measures fail after 72 hours 1
• Target blood patch at the level of identified CSF leak when possible 1
• Monitor for rebound headache post-procedure (occurs in ~25% of patients) 1

If CVT is identified:

• Immediate anticoagulation is indicated even in presence of small subdural collections 1
• The case report demonstrates that anticoagulation can be safely continued despite hemorrhagic complications when managed with osmotic therapy 1