Discussion

Herein, we present a prospective series showing the variety and incidence of neurological disease associated with air traffic. Our sample is large and based on a representative population: an international airport with almost 50 million passengers a year. Since our hospital is the reference centre for medical emergencies at the airport, it is unlikely for us to overlook major medical problems occurring during the flight or after landing, with the exception, perhaps, of patients with onset of symptoms after leaving the airport. This is noteworthy, as most of the studies on medical and neurological problems linked to air traffic are solely focused on in-flight emergencies, while in our series, 58.7% arose after landing.

As suggested elsewhere,4 we confirm that neurological problems are very common in this setting, accounting for 18.35% of the patients transferred from the airport to our ED. The most frequent profile is a middle-aged male patient with a history of a long-haul flight, especially in patients presenting with seizures.

Seizures were the most common complaint in our group, and the use of recreational drugs was significantly associated with seizures. Interestingly, for the vast majority, this episode was the first seizure of their lives. We may therefore suggest that the use of drugs in the setting of long international flights (with sleep disruption and possibility of deprivation) is a risk factor for first seizures to occur in vulnerable subjects. Drug screening is mandatory in any patient with seizures or altered mental status of unknown origin in the setting of air traffic and may be critical for potentially fatal diagnoses as cocaine packs rupture. As for epileptic patients, a study by Trevorrow found that a previous high seizure frequency, fear of having a seizure and history of seizures in previous flights were the main factors in predicting a seizure following a flight.11 The use of drugs and sleep pattern were not investigated. In our experience, among the 13 epileptic patients who were admitted for a seizure, almost all patients reported a possible trigger, and non-adherence to antiepileptic drugs was strikingly frequent. This stresses the importance of the education of epileptic patients, who should be instructed to remain adherent and avoid other triggers for seizures in the vulnerable period of air travelling, especially if their disease is poorly controlled.

We found common causes of stroke to be most frequent in air-traffic-associated ischaemic stroke, with a surprisingly high proportion of high-grade carotid stenosis, while only one patient suffered a typical economy class stroke. It has been suggested that the hypobaric and hypoxic environment inside the aircraft may cause ischaemia in patients with reduced vascular reserve or arterial dissection.5 Even if the number of cases in our series is too low, we suggest that neurologists give some words of caution to patients with known high-grade stenosis who plan to fly, because of the potentially increased risk of stroke linked to air travel. On the other hand, in our series, prompt referral to the ED allowed treatment with intravenous thrombolysis in a large proportion of these patients, favouring a good outcome in most cases. Cooperation among the airport medical services, our hospital emergency medicine physicians and neurologists is essential in this setting and may be further promoted by the implementation of a stroke code, currently in use in the region of Madrid.

Finally, the subgroup of patients with other diagnoses is rather heterogeneous, with the toxicity of recreational and therapeutic drugs and non-organic symptoms being the most common diagnosis. Two patients sought medical attention presumably unavailable in their countries of origin. This phenomenon is not uncommon in a country such as Spain with universal healthcare, including care for tourists and non-residents. We did not record any cases of other diseases specifically linked to air traffic, recently described in scientific literature, namely airplane-headache related to atmospheric pressure changes. In addition, while other studies found syncope and dizziness to be the most common neurological complaints,2 4 these symptoms were rarely reported in our series. It is most likely that these patients were treated by airport medical services and emergency medicine physicians without neurological consultation.

A limitation of our study is the lack of information regarding flight diversions, or if therapeutic measures were applied on-board when the onset of symptoms was during the flight. Neurologists and other physicians on-board may be able to handle some serious neurological problems on-board (figure 1). In cases of repetitive or prolonged seizures and status epilepticus, a sublingual or buccal tablet of lorazepam, intranasal midazolam or rectal diazepam may be efficacious; these carry a smaller risk of central nervous system depression than intramuscular diazepam and are easier to administer.12 13 In cases of impairment consciousness, a lateral head-down position may prevent aspiration and an oropharyngeal airway may be placed to deliver high-flow oxygen. Most medical kits on-board include oral or intramuscular antiemetics, analgesics and sedatives to treat nausea, pain and agitation.4 For agitation, we recommend using benzodiazepines instead of haloperidol, which may provoke serious adverse events in case of cocaine intoxication, such as seizures and extrapiramidal reactions (box 1).

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Figure 1

Proposed algorithm for the management of stroke, seizures and altered mental status on-board.

As for stroke, it is critical for the aircrew (and, perhaps, for the physicians on-board) to recognise stroke symptoms and signs. Simplified stroke scales for non-physicians (such as the Cincinnati Stroke Scale)14 may be helpful for the training of aircraft personnel in this regard. In case of stroke, administration of antiplatelet or anticoagulant drugs is strongly discouraged. An emergency call to the airport medical services, with activation of a stroke code and prompt referral to the nearest Stroke Unit immediately after landing, may be time- and life-saving. Diversion of the flight or unscheduled landing must be considered on suspicion of stroke, altered mental status, and prolonged or multiple seizures.

This study suggests that air travel may induce a variety of neurological problems; seizures and stroke rank first and second, respectively, on the list. We observed an association among the use of recreational drugs and first seizures, and recognition of common triggers in seizures occurring in epileptic patients. We found a strikingly high proportion of high-grade carotid stenosis, whereas economy-class stroke syndrome was rare. Cooperation among airport medical services and in-hospital emergency services is crucial in time-dependent diseases as stroke.