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10. Central Nervous System Disorders

CT scan of patient with intracranial air. Patients with intracraniel air are not accepted on commercial flights because  the lower cabin pressure at cruising altitude will result in the expansion of the trapped air.

Photo: Dept. of Radiology,

Rigshospitalet


General


The main aeromedical problems associated with this group of disorders all arise from conditions involving increased intracranial pressure (whether due to infarct, haemorrhage, trauma, tumour, or infection) and disorders with intracranial air.


Patients may not travel by commercial flight with increased intracranial pressure

or intracranial air.


Concerning disorders with increased intracranial pressure (ICP)

Flying at normal cruising altitude with the cabin pressure at ¾ atm will aggravate the effect of increased ICP with risk of incarceration (brainstem compression). In cases where increased intracranial pressure is suspected (headache, vomiting, confusion, low pulse and high blood pressure, etc.), a CT or MR scan should be carried out, partly to establish the nature of the complaint, and partly the degree of oedema and degree of midline shift, and thereby give an indication of increased ICP.


Concerning disorders with intracranial air

A CT scan is excellent at revealing intracranial air, which can be seen after serious head trauma with fracture or after craniotomy. If the amount of intracranial air is not at a minimal level, the patient will not be able to travel by commercial flight. The reason being that while the aircraft climbs, the cabin pressure will be reduced and the intracranial air will expand and press on the surrounding cerebral tissues.


Air transport of patients with increased ICP or intracranial air

If such a patient, because of a lack of onsite treatment facilities, has to be transported by air, it has to be with an air ambulance, flying with the cabin pressure at 1 atm (sea-level flight). Patients with increased ICP have to be placed in the aircraft with their head towards the nose of the plane, as the effect of the aircraft’s power is stronger at take-off than at landing. Furthermore, the bedhead should be elevated 30°.

If there are signs of seriously increased ICP, the patient can be treated with IV hypertonic sodiumchloride (1 meq/ml, 50-100 ml) or Manitol 20%, which will reduce the ICP for some hours. The patient must be escorted by an anaesthetist and anaesthetic nurse.


Patients with neurological conditions (myopathies, cervical myelopathy decompensated myasthenia gravis, ALS, polio, Parkinsons disease, etc.) that cause limited muscle power need different types of assistance such as an escort, a wheelchair at the airport, oxygen during the flight, NIV (non-invasive ventilation), a ventilator, etc.



Stroke


About 85% of strokes consist of cerebral infarctions, 10% of intracerebral haemorrhages, and 5% of subarachnoid haemorrhages.


Cerebral infarctions and intracerebral haemorrhage

Patients with infarcts, where all the neurological symptoms have disappeared quickly, will normally be accepted on a commercial flight after 4-7 days, seated and unescorted. Airline companies may differ with regard to the conditions for accepting these patients.

Patients who continue to have neurological symptoms and signs, such as hemiparesis, will normally be accepted on commercial flights after 7-10 days, if there are no signs of increased ICP and the patient’s condition is good and stable. A CT or MR scan should be done to confirm the localisation and size of the infarct. Serious infarct oedema in cases of cerebral or cerebellar infarction will normally subside within 6-7 days.

All patients who have had a cerebral infarct should immediately start prophylactic treatment with aspirin (ASA) 75-150 mg/day or clopidogrel 75 mg/day. Clopidogrel requires loading with 300 mg.

The patients should also receive 24-48 hours of EKG monitoring to reveal intermittent AF. Patients who have intermittent or manifest AF should start oral anticoagulation 48 hours after the infarct, later if the infract is large.

For patients with persistent neurological symptoms, the method of transportation depends entirely upon their clinical condition. Patients with severe paresis may need stretcher transport. Patients who have problems swallowing should have a gastric tube.

Air ambulance transportation with accompanying anaesthetist and anaesthetic nurse may also be necessary if the patient is respiratory insufficient or unstable after the observation period.


Subarachnoid haemorrhages

If the case is not hopeless, a patient with a recent subarachnoid haemorrhage from an aneurysm should have the aneurysm closed within the first couple of days with an endovascular procedure or an operation. Today most aneurysms will be treated with endovascular coiling and fewer with craniotomy and clamping of the aneurysm. If reasonable treatment facilities are available at the location where trauma occurred, the patient should be examined and operated there.

If reasonable treatment facilities are not available locally, repatriation should be undertaken by air ambulance and the patient should be escorted by an anaesthetist and an anaesthetic nurse. If the initial bleeding is minimal, a case can be made for flying the patient at normal cruising altitude (with cabin pressure at ¾ atm), but if there are signs of increased ICP, the aircraft must fly at an altitude where the cabin pressure can be maintained at 1 atm (sea-level flight).

In those cases where thorough and, perhaps, repeated examinations by CT or MR scan and arteriography reveal no source of bleeding, the risk of a new bleed is small and the prognosis considerably better. These patients may, as a rule, be transported in a reclining position by commercial flight, accompanied by a physician after approximately 14 days, or, in some cases, they may travel unescorted in the seated position after achieving full mobilisation without symptoms, normally after a another week.

When the patient is being moved to treatment, consultation with the relevant neurosurgical department is recommended in order to ensure unanimity concerning the indication of surgery and transportation criteria, etc.



Transient Ischemia Attack (TIA)


All patients who have had a TIA should immediately (after a CT that excludes haemorrhage) start prophylactic treatment (see above). Be aware that the term TIA is often used incorrectly in cases with unaccountable, unspecific, and transient symptoms. The TIA diagnosis should, however, be reserved for cases with transient hemiforme (half-sided) deficits without loss of consciousness. Per definition, the attack can last for 24 hours, but usually it lasts less than 30 minutes.   

All patients who have had TIA – not only those who have suffered several TIA’s – have a risk of developing new emboli. Before flying, it is recommended that these patients, besides the prophylactic treatment, should have as a minimum a CT scan or, if possible, a MR scan with diffusion-weighted images (DWI) and a Doppler ultrasound scan of the carotid arteries.  Furthermore, an ECG monitoring should rule out atrial fibrillation.

After a single TIA with rapid and complete remission within 24 hours and where the scan has shown no infarct or bleeding, the patient will normally be accepted unescorted on a commercial flight after a few days.



Epilepsy


In general, a patient with epilepsy should receive optimal treatment and have the medication well-adjusted before air travel. The stress related to waiting time at airports, lack of sleep, the changing of time zones, etc., can increase the risk of an attack. Using a supplementary benzodiazepine from the day before travelling to the day after arrival as prevention against attack is recommended in some patients for long journeys, especially with different time zones. 

An epilepsy patient who has suffered an attack will normally be accepted on a commercial flight 24 hours after the event.

Cases of frequent or several attacks must be evaluated individually.

If a patient has recently been diagnosed with epilepsy (and other neurological disorders have been excluded), the airline companies often demand a physician as an escort.



Sleep apnoea


Patients with moderate to severe sleep apnoea may bring their CPAP machine in the cabin if agreed to by the airline company.



Intracranial infections


Patients suffering from intracranial infections may be transported by commercial flight when normal ICP has been assured, that they are no longer a source of infection, and their circulation and respiration are stable. This applies both to patients with meningitis, encephalitis, or a brain abscess. Disposition and escort are subject to the clinical condition of the patient.


In case of a lack of local treatment facilities, a patient with intracranial infection and increased ICP will need to be evacuated by air ambulance, maintaining sea-level cabin pressure.



Intracranial tumours and hydrocephalus


Both intracerebral and extracerebral intracranial tumours, especially when malignant, can cause a rapid development of increased ICP. This is partly due to the growth itself and partly to oedema in the tumour’s surroundings or a blockade of the ventricle, causing hydrocephalus. If the tumour is first diagnosed during an overseas trip, the patient is at risk of being “trapped”, because the increased ICP will result in commercial airlines refusing to transport him or her.

Nevertheless, the oedema surrounding the tumour can be reduced by the administration of high doses of steroids (for example, prednisolone 150 mg/day) for a short period. If this normalises the ICP and the patient can be accepted on a commercial flight, it is important that the patient travel back immediately before the ICP rises again.

Before travelling by air, patients with hydrocephalus need a ventricular drainage.



Head injury


Concussion

In cases of mild concussion, there is rarely cerebral oedema; therefore these patients may travel by air as normal passengers on commercial flights as soon as they are mobile without symptoms, usually within 1-2 days.

In cases of more severe concussion with loss of consciousness for more than 3-5 min., it is necessary to do a CT scan to exclude intracranial damage. Concussions with accompanying oedema may be subject to increased ICP for several days. Travel by commercial flight must be delayed until the patient is without signs of increased ICP and is fully mobilised without symptoms. The patient will then normally be able to travel, seated and unescorted.


Skull fractures

Non-dislocated skull fractures do not give rise to problems. Only attendant lesions of the brain (contusions or hematoma) or dura will lead to restrictions by commercial flights. Fractures accompanied by the tearing of the dura, with the loss of spinal fluid through the nose, pharynx, or ear and eventually with intracranial air, present a serious aeromedical problem. Such a defect will always be a gateway for infection. There will be a strong outward flow of cerebrospinal fluid during ascent due to the change in cabin pressure, and, during descent, it is even possible for air together with blood/secretion to be sucked in through the nasal fossae or the middle ear if the original fracture involves these areas.

If loss of spinal fluid does not stop spontaneously within 1-2 weeks, the patient should be operated on to close the defect. A patient suffering from a dural lesion with loss of spinal fluid will not be accepted on commercial flights. Should transportation be unavoidable, e.g. because of the lack of treatment facilities, this must be undertaken by air ambulance maintaining sea-level pressure in the cabin.


A patient with a non-dislocated cranial fracture should be placed under observation for a few days before flying in order to ensure that there are no attendant cerebral injuries or dural lesions. If the patient, hereafter, is mobilised without symptoms, the journey can be made, seated and unescorted, by commercial flight.



Craniotomy


After brain operations, there will always be a certain degree of oedema together with small air pockets that will gradually be reabsorbed. Patients will not be accepted on board commercial flights until there is no longer air or oedema in the brain, which may take several weeks. Transportation and the need for an escort must be evaluated according to the patient’s clinical condition.



Lumbar puncture


After a lumbar puncture, the patient can fly in principal. Patients who develop a headache due to a lumbar puncture need to wait until the symptoms disappear before flying, possibly after a blood patch.




 


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