What is the most likely etiology of a postpartum headache that worsens with upright position and improves with recumbency, with MRI findings of postcontrast pachymeningeal enhancement, in a patient who recently underwent epidural anesthesia?

Most Likely Etiology: Cerebrospinal Fluid Leak Following Epidural Anesthesia

The most likely etiology in this patient is a cerebrospinal fluid (CSF) leak following epidural anesthesia, which classically presents with positional headache (worse upright, better supine) and pachymeningeal enhancement on MRI. 1

Clinical Reasoning

Classic Presentation of Post-Dural Puncture Headache

• The positional nature of this headache is pathognomonic for intracranial hypotension from CSF leak: headache worsens when upright and improves with recumbency, typically within 20 seconds of lying down 1, 2
• Post-dural puncture headaches occur in 2-8% of patients after epidural anesthesia and typically develop within 5 days of the procedure 1, 2
• This patient's 4-day timeline (1 week postpartum, symptoms for 4 days) fits perfectly within the expected window 2
• The headache location "near the top of her head" is consistent with the typical frontal or vertex distribution of post-dural puncture headache 1

MRI Findings Confirm CSF Leak

• Pachymeningeal enhancement overlying the cerebral convexities is a hallmark imaging finding of intracranial hypotension from CSF leak 1
• The ACR Appropriateness Criteria (2024) specifically identifies diffuse pachymeningeal enhancement as one of the key intracranial findings in spontaneous intracranial hypotension 1
• This enhancement pattern results from compensatory dural venous engorgement in response to decreased CSF volume 1

Why Other Diagnoses Are Less Likely

Cerebral Venous Thrombosis (CVT):

• While CVT can occur postpartum and may show dural enhancement, the headache is typically position-independent and severe 1
• The case report describing CVT after epidural anesthesia specifically noted "sudden position-independent severe headache" 1
• CVT typically presents with progressive neurological deterioration, seizures, or focal deficits, none of which are present in this patient 1, 3
• Unilateral (ipsilateral) dural enhancement is more suggestive of CVT, whereas this patient has bilateral convexity enhancement consistent with diffuse intracranial hypotension 1

Idiopathic Intracranial Hypertension:

• This condition causes headache that worsens when lying down, the exact opposite of this patient's presentation 1
• Pachymeningeal enhancement is not a typical finding in idiopathic intracranial hypertension 1

Migraine Without Aura:

• Migraines do not have the characteristic positional component seen in this patient 2
• Pachymeningeal enhancement is not associated with migraine 1

Subarachnoid Hemorrhage:

• Would present with sudden, severe "thunderclap" headache at onset, not gradual mild headache over 4 days 4
• Neurological exam would likely show meningismus or focal deficits 4

Management Approach

Initial Conservative Management

• Most post-dural puncture headaches resolve spontaneously within 1 week without treatment 1, 2
• Conservative management includes bed rest, adequate hydration (oral or IV if needed), and multimodal analgesia with acetaminophen and NSAIDs 2
• Caffeine (up to 900 mg/day) may be offered within the first 24 hours of symptoms 2

When to Escalate Treatment

• Epidural blood patch should be considered if symptoms are severe or do not begin to resolve by 2-3 days post-dural puncture 1, 2
• The blood patch has a high success rate, with marked decrease in pain intensity approximately 4 hours after the procedure 2, 5
• The blood patch works by creating a tamponade effect on the thecal sac, stopping CSF leak and allowing the dural defect to heal 5

Important Caveat About CVT

• While CSF leak is most likely, cerebral venous thrombosis remains a critical differential that must not be missed, as it can initially be misdiagnosed as post-dural puncture headache 1, 3
• If the patient develops position-independent headache, neurological deterioration, seizures, or fails to improve with conservative management, urgent venographic imaging (CT venography or MR venography) is mandatory to exclude CVT 1
• The case literature documents that CVT can develop as a complication of prolonged intracranial hypotension from CSF leak 3

Monitoring for Complications

• Post-dural puncture headache can lead to complications including chronic headache, subdural hematoma, and cerebral venous sinus thrombosis 2
• Close follow-up is essential, with clear return precautions for worsening symptoms, focal neurological deficits, or seizures 6, 7