A 55-year-old woman presented with a five-week history of progressive bilateral occipital headaches and neck pain. This began after an abrupt neck movement while using a computer. The occipital headaches were exacerbated by sitting up or standing and worsened throughout the day. There was associated facial pain. Self-management for sinusitis was ineffective; a CT sinus was normal. There was no preceding trauma, surgery or lumbar puncture. She then developed diplopia and increasingly severe headaches, leading her to present to the emergency department. Blood tests were normal. Cervical spine x-ray showed end-plate osteophytes in the upper cervical spine. CT brain showed thin bilateral subdural effusions, dural venous sinus distension and an apparently enlarged pituitary gland, consistent with intracranial hypotension.

Magnetic resonance imaging (MRI) brain findings supported those of the CT. An MRI scan of the spine showed an anterior epidural effusion from C1 to L3 (Figure 1). She was admitted for an epidural blood patch, resulting in resolution of her symptoms.

Figure 1: MRI of brain and spine without gadolinium.

Discussion

Spontaneous intracranial hypotension is an important but unusual cause of daily headache, with an incidence of five in 100,000 (approximately half of the incidence of spontaneous subarachnoid haemorrhage).1 It affects more women than men. The average age of onset is in the early 40s.2

An orthostatic headache is the hallmark of intracranial hypotension. The headache is bilateral, occipital and occurs with sitting up or standing. Reduced CSF volume causes sagging of the brain and stretching of important structures, leading to the corresponding symptoms: neck pain; meningism;3 cranial nerve deficits. In the case of this patient, the facial pain can be explained by traction of the trigeminal nerve, and the diplopia by traction of the abducens nerve.2,3

In the absence of trauma, an important cause of intracranial hypotension is a spontaneous spinal CSF leak (Figure 2).4 Spontaneous spinal CSF leaks are caused by an underlying weakness of the spinal meninges or the presence of osseous spurs that pierce the dura. In one-third of cases, a mildly traumatic event such as coughing or twisting has been identified as a precipitant.5 Underlying dural defects include meningeal diverticula (associated with neurofibromatosis type 1), simple dural rents or, rarely, the absence of dura mater.2 In this patient, the combination of cervical osteophytes and the abrupt neck movement may have caused a dural rent. Genetic connective tissue disorders may affect the integrity of the dural extracellular matrix and predispose to spontaneous spinal CSF leakage.2,6

Figure 2: Diagnostic criteria for headache due to spontaneous spinal CSF leak and intracranial hypotension according to the International Classification of Headache

If intracranial hypotension is suspected, an MRI brain and spine should be performed to confirm the diagnosis and to source the leak. A mnemonic for MRI findings of intracranial hypotension is detailed in Figure 3.2 Pachymeningeal enhancement may lead to investigations for infective and other causes of enhancement, so recognition of the orthostatic headache syndrome is key. A lumbar puncture for CSF opening pressures can be done but may worsen symptoms. Myelography can be used to identify the site of CSF leak if the MRI does not.

Figure 3: Diagnostic criteria on MRI brain uses the mnemonic SEEPS.

Initial treatments include caffeine, high fluid intake and lying flat. Epidural blood patches (autologous blood infusion into the epidural space) increase CSF volume, and potentially clot to seal a defect.2,5 Repeated blood patches may be necessary. If symptoms are refractory, interventions include epidural fibrin glue, continuous epidural saline infusions; surgical repair is an option if a CSF leak site is identified.5

Overall, intracranial hypotension is an important and treatable cause of headache that should be considered in those presenting with an orthostatic headache.

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