Greater Occipital Nerve Block for Spontaneous Intracranial Hypotension

Spontaneous Intracranial Hypotension (SIH) is a debilitating neurological disorder caused by a cerebrospinal fluid leak (CSF), with an estimated incidence of 5 per 100,000 persons per year, of which mostly women between the ages of 35 years and 55 years. The typical presentation is moderate-to-severe orthostatic headache and several other possible neurological symptoms, that significantly impact patients' quality of life.

Treatment of SIH usually starts with conservative measures, consisting of strict supine bed rest, hydration, caffeine, and simple analgesics. The vast majority of patients will require invasive treatments for their CSF leak, such as epidural blood patches, fibrin glue patches, endovascular coiling, and/or surgical repair. These specialized treatments are only offered in tertiary care centers and require specialized personnel and resources, which implicates a certain waiting time for the patients before permanent treatment is offered. In the meantime, due to the lack of an effective and accessible alternative, patients continue to suffer.

The greater occipital nerve block (GONB) has been reported as a simple, safe, and effective treatment to provide short-to-intermediate term relief of migraine, cervicogenic headache, cluster headache, occipital neuralgia, and more recently, post-dural puncture headaches (PDPH). As the pathophysiology of intracranial hypotension caused by SIH or PDPH is very similar, it is stipulated that the effect of GONB will be similar for SIH patients. However, to date, no studies exploring the efficacy of GONB for SIH have been performed.

The investigators propose to do a prospective observational study to explore the outcome of GONB for SIH. GONB can serve as a bridge therapy to control the debilitating headache of SIH while patients are awaiting permanent SIH treatment. Moreover, GONB can be performed by physicians of different specialties including neurology, which makes it an accessible treatment for all patients. Lastly, by offering better symptom control, this intervention could potentially restore patients' ability to work and reduce healthcare costs.

This a prospective observational study on 34 patients with SIH, recruited from the Toronto Western Hospital Intracranial Hypotension Clinic. Patients will receive an ultrasound-guided bilateral GONB of 5 mls of injectate of mix of local anesthetic with steroid. There is no comparator. Primary outcome is the change in intensity of headache at 30 minutes post-intervention. Secondary outcomes are change in intensity up to day 14 post-intervention, onset of headache, sitting endurance, change in SIH-associated central nervous system (CNS) symptoms, emotional functioning, patient satisfaction, analgesic consumption and side-effect, up to 14 days post-intervention

Eligibility Criteria:
Inclusion criteria

1. Adults of \> 18 years of age
2. Diagnosis of SIH, according to the International Classification of Headache Disorder (ICHD-3) classification (2)
3. Characteristics of pain:

   1. Baseline pain intensity NRS \> 4/10 (in upright position)

Exclusion criteria

1. Contraindications to GONB: ongoing infection (systemic or located at the site of injection), intake of anticoagulants (not aspirin), allergy to injectate, contra-indication to injectate of steroids
2. Any significant cognitive or language barrier that impedes participation
3. Patients taking opioid medications with daily Oral Morphine Equivalent (OME) of 50 mg or higher
4. Patient refusal