Postdural puncture headache in obstetric patients

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION

PDPH is described by the International Headache Society as headache that occurs within 5 days of a lumbar puncture, which is usually associated with neck stiffness and/or subjective auditory symptoms, and that shows spontaneous resolution within 14 days or responds to an autologous blood patch.⁷ It typically exhibits onset within 72 hours of dural puncture either inadvertently during attempted epidural analgesia for labour or deliberately during spinal anaesthesia for operative interventions. It is estimated that PDPH follows ∼1% of all neuraxial blocks for labour and delivery.^2,8 Certain characteristics of parturients, namely sex and young age, may predispose them to the development of PDPH, as may factors such as previous PDPH, bearing down during the second stage of labour, and the neuraxial technique itself.¹

The hypothesised aetiology of the headache is slow cerebrospinal fluid (CSF) leak through the defect in the meninges, causing intracranial hypotension with resultant traction on pain-sensitive structures and reactive venodilatation. The headache is classically bilateral occipito-frontal in location (less commonly in the temporal region or vertex), dull aching or throbbing in character, and of variable severity. A distinctive characteristic of PDPH is its orthostatic nature, with manifestation of symptoms in the upright position and relief on assuming recumbence. The headache may show exacerbation on coughing or straining, and >50% of cases may be associated with additional symptoms such as nausea, photophobia, tinnitus, or vertigo.² It is worth noting, however, that atypical presentations that lack a postural component, that have an immediate or delayed onset or a protracted course, or that present as isolated interscapular or back pain with radiation to the upper limbs, have been reported.⁸

COMPLICATIONS

Subdural haematoma is an uncommon consequence of dural puncture and PDPH that may have a delayed presentation and carries a mortality rate of about 13%.² The proposed mechanism is shearing of the subdural veins caused by sagging of the brain secondary to the low CSF pressure. Intracranial hypotension may additionally lead to vascular stasis and cerebral venous thrombosis. Convulsions, cerebral infarction, cranial nerve palsies (most commonly of the sixth nerve, causing diplopia), and chronic headache states have also been described.¹

MANAGEMENT

The management of PDPH should be instituted in liaison with the patient’s anaesthetic team. Treatment for mild cases is typically initiated with supportive measures while allowing time for spontaneous healing of the dural perforation. Bed rest may provide symptomatic relief but there is no evidence that it alters the clinical course, and its benefits must be weighed against the heightened risk of venous thromboembolism during puerperium. Although frequently encouraged, the role of increased fluid intake to replenish the lost CSF remains unclear.⁹ Pharmacological treatment includes simple analgesics like paracetamol and non-steroidal anti-inflammatory agents, and antiemetics. Caffeine (given orally or intravenously) promotes cerebral vasoconstriction and was found to reduce the incidence of persistent PDPH and the need for supplementary conservative interventions.¹⁰ Other drugs such as gabapentin, hydrocortisone, and theophylline may reduce pain severity scores, but evidence for their role in the treatment of PDPH has yet to be established.¹⁰

Patients with moderate to severe PDPH may require further anaesthetic intervention, namely an epidural blood patch, which is the mainstay of treatment of PDPH and involves the aseptic collection and injection of autologous blood into the epidural space. The blood clot creates a seal to the dural puncture, thus arresting the CSF leak. The procedure has an initial success rate of up to 70%¹ but may need to be performed more than once to produce relief from the headache. Transient post-procedural back pain is reported by some patients. An epidural blood patch also carries the same risks of epidural catheter insertion, including that of infection or causing another dural puncture.

WHEN TO REFER

Both clinicians and patients should remain vigilant for ‘red flag’ features that may indicate more sinister conditions and that should trigger emergency neurology referral and/or neuroimaging. These include: loss of the postural element, unilaterality, altered sensorium, uncontrollable vomiting, signs of infection, the development of convulsions, focal neurological features, or the persistence, progression, or recurrence of symptoms. It is important to remember that dual pathology may exist, and that the clinical picture of evolving cerebrovascular stroke may overlap with that of PDPH, making a high index of suspicion essential when assessing these patients (Box 1).