Written by Dr Hemant Mehta
A 60-year-old man with no existing comorbidities took a 12-hour long, non-stop flight from New York to Mumbai and began to suffer from a new type of intense headache that he had not experienced before. The headaches did not subside even with persistent use of analgesics combined with conservative management, frequent hydration and increased bed rest over the course of two weeks after travel.
Have you also had headaches after a long flight and wonder why they happen when you were in a fine fettle before boarding the aircraft? Airplane headaches can have varied causes, depending on factors such as sinus barotrauma, which is 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.
Why the headaches happen?
The intensity of headache is maximum during take-off and landing, which usually subsides within 30 minutes. The most common causes of airplane headache are 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 (cerebro-spinal fluid) leak due to a dural rent or tear.
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 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 equalise 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 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 per cent), followed by cervico-thoracic 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 per cent 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 centre. Follow-up MRI scans may be required to establish successful treatment.
What about complications?
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 contrast spread techniques 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.
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Hypothesis states that an epidural blood patch causes a sealant effect on the site of the tear. Another hypothesis is that it causes acute compression of the 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, a smaller volume of blood should be injected (when compared to the lumbar levels) to avoid spinal cord compression. Around 5-8 ml 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.
Other underlying reasons for headache
Differential diagnosis can be chronic fatigue syndrome, other forms of tension headache and migraine, secondary causes of headache — either underlying systemic or neurologic disease.
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The prevalence of chronic daily headache internationally is 4 per cent. The pathophysiology of headache is likely to be mediated by vasodilation of arteries and cervical nerve root delivery of pain-mediated signals. Targetting the early signalling pathways and modulating neuropeptide levels for pain management form the basis of neuromodulation therapy. They help in re-programming the brain’s response to noxious stimuli.