Airplane headache can have varied causes which depend on factors such as sinus barotrauma, as a result of changes in barometric pressure between the atmosphere and pressure within the intranasal sinuses. This in turn depends on factors such as speed of the aircraft, changes in cabin pressure, changes in weather pattern and maximum altitude reached. The intensity of headache is maximum during take off and landing, which usually subsides within 30 minutes. Most common cause of airplane headache is due to jet lag which can be attributed to disruption in circadian rhythm, fatigue, lack of sleep and dehydration. This may mimic spontaneous intracranial hypotension that occurs after a CSF leak due to a dural rent.
In 4-8 per cent of air travellers, the headache may persist from days to weeks. In such cases, when the headache is not alleviated by conservative pharmacological therapy with NSAIDs, triptans, rest and rehydration, further research into other causes is warranted. Such headaches may occur due to trauma to the head or neck during take off or landing which may cause a minor CSF leak. Sometimes, violent coughing, or chiropractic maneuvers of the neck to equalize cabin pressure such as yawning, clicking of ears, hyper-extension of jaw muscles, may cause tearing of meninges with small degrees of force. Abnormal position of the head or neck during, sudden jerks during air travel may also cause minor trauma and a CSF leak, which can go undetected.
According to a recent study, the most common leak location is the thoracic spine (41%), followed by the cervicothoracic junction (25 per cent), the cervical spine (14 per cent), and the lumbar spine (12 per cent). In such cases, diagnosis depends on brain MRI, which may reveal enhancement of the meningeal lining, or spinal fluid leaking out of its normal location. CT myelogram may reveal the site of leak directly. If the headache is not treated my conservative management, such as bed rest, caffeine or increased fluid intake, analgesics and anti-inflammatory agents, the next step of treatment is an epidural blood patch which gives immediate relief of symptoms within 24 hours.
Epidural blood patches are considered the first line of treatment in patients with spontaneous intracranial hypotension which are not responsive to pharmacologic treatments. In such cases, clinical and imaging features can confirm the diagnosis for which a high resolution MRI is needed. However, it should be noted that although CSF leaks may not be readily apparent on imaging, a suspected leak is important to consider since it is fixable and 90% response is seen to a single epidural blood patch. However, experienced hands are required to perform the procedure, fluoroscopic guidance, C-arm guided technique, post op follow up pain clinic are other requirements to perform the procedure at a fully equipped center. Follow up MRI scans may be required to establish successful treatment.
Commonly cited complications include cranial nerve palsy, changed mental status, subdural hematoma, seizures , and transient bradycardia . Serious adverse events include compression of nerve roots, and chemical meningitis. At the cervical level, spinal cord compression becomes the most feared complication. Loss of resistance technique is usually used to find the epidural space, which is confirmed using contrast spread under fluoroscopy. Four reports used CT guidance along with spread of contrast to confirm needle location, most reported immediate relief. However, this lasted for a short period of time (range 1-7 days). Cervical EBP in these patients then led to long-term relief.
Hypothesis states that an epidural blood patch causes a sealant effect on the site of dural tear due to dural tamponade by blood clot. Another hypothesis is that it causes acute compression of thecal sac due to increased hydrostatic pressure. It is more effective in cervical CSF leak, lumbar epidural patches may need multiple sittings and partial relief of symptoms. Given the narrow diameter of the cervical epidural space, particularly above the C6 level, smaller volume of blood should be injected (when compared to the lumbar levels) to avoid spinal cord compression, around 5-8ml of autologous blood can be injected to the narrow space of 0.5cm especially in the upper cervical levels.
MRI of cervical spine has to be assessed prior to cervical EBP to evaluate the epidural space at the cervical level and allow for a safer procedure. Other differential diagnosis can be chronic fatigue syndrome, other forms of tension headache and migraine, secondary causes of headache — either underlying systemic or neurologic disease. The prevalence of chronic daily headache internationally is 4%. The pathophysiology of headache is likely to be mediated by vasodilation of arteries and cervical nerve root delivery of pain mediated signals.
Thalamo-cortical circuits are found to play a role in the pathophysiology of headache and the release of neuropeptide headache mediators such as calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) . Targeting the early signalling pathways and modulating neuropeptide levels for pain management is the basis of neuromodulation therapy. They utilise the gate control theory and help in re-programming the brain’s response to noxious stimuli. It is helpful in narcotic refractory conditions. It is usually done in multiple settings.
Behavioural therapy is an another modality that incorporates biofeedback and CBT for relaxation and pain modulation.
The author is Director, Anesthesia and Pain Management, Sir HN Reliance Foundation Hospital. Viws expressed are personal.
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