Disturbances of Awareness or Consciousness

Dizziness is a symptom with numerous causes. Determine what the patient means by "dizziness" by asking what they feel such as: about to pass out (pre-syncope), a spinning sensation or illusion (vertigo), trouble walking without vertigo or pre-syncope (dysequilibrium), lightheadedness with or without anxiety. Not all dizziness involves vertigo (spinning). Check for red flags that may indicate an ominous cause: fever, stiff neck, head trauma (more than mild), cranial nerve dysfunction, severe headache, difficulty mentating, seizure, double vision, difficulty swallowing or talking, severe depression (suicide risk), suspected toxin, medication or illegal drug exposure, infection, alcohol (subdural), chest pain, difficulty breathing, severe hypertension or hypotension, or history suggestive of DCS. If vertigo (spinning) is the only symptom and head movement triggers it then Benign Positional Vertigo is the most likely diagnosis. Other common causes of dizziness in the military population include: heat exhaustion, motion sickness, dehydration, head trauma, vasovagal, toxin exposure, electrolyte disturbance, drugs, alcohol, hyperventilation, sleep deprivation and psychiatric. Aviators may experience "dizziness" while flying secondary to various illusions or hypoxia.

Headache in the aviation environment can be distracting to the point that safety of flight could be compromised. Medications used to treat headache can have side effects with similar concerns. The most common headache is tension type characterized by gradual onset, steady bilateral pain that is not throbbing and is long lasting. Similar headaches can be associated with stress, dehydration, fasting, withdrawal from coffee or medications, exposure to a toxin, associated with an infection, endocrine dysfunction, following head trauma, sleep depravation, or depression. Migraine is a type of headache characterized by unilateral throbbing pain that lasts for hours to days and is associated with nausea, vomiting, photophobia, sound sensitivity, is aggravated by physical activity and may be preceded by an aura. Visual aura that is most described is the fortification spectra (see figure 1). Cluster headaches are severe and recurring but fortunately usually short in duration. The pain is boring, sharp around an eye that is red with a droopy eyelid, lacrimation, nasal congestion and often occurs during REM sleep. The headache associated with a sinus infection is characterized by local pain behind the eyes with malaise, nasal discharge and fever. The vast majority of headaches are benign but bacterial meningitis, subarachnoid hemorrhage and brain tumors do occur in the military population. Headache red flags include: fever, stiff neck and "explosive" onset over several minutes with nausea and vomiting, alterations in consciousness, third nerve palsy or any neurologic dysfunction.

Motion Sickness in the aviation environment is generally detected and treated early in flight training. Symptoms include cold sweating, nausea, drowsiness, yawing, facial pallor, salivation, lethargy, apathy, headache and vomiting. Airsickness is motion sickness in the flight environment and can cause poor flight performance and affect motivation. A Self Paced Airsickness Desensitization Program (SPAD) at the Naval Operational Medicine Institute in Pensacola has a 60% success in treating motion sickness (see figure 2).

Head Trauma resulting in loss of consciousness (LOC) or post traumatic amnesia (PTA) can be classified as PTA+LOC: minor <5 min, mild >5min but <1hr, moderate 1-24 hrs, and severe >24 hrs, traumatic brain injury. A careful and accurate estimation of this time is important because it determines how long an aviator must be observed before a waiver to return to flying can be submitted following a head injury. Following head trauma even without LOC or PTA, posttraumatic symptoms can occur and include: headache, dizziness, sleep disturbance, blurred vision, poor concentration, memory disturbance, irritability, depression, and personality change. Posttraumatic seizures are the most significant aeromedical concern following head trauma. The risk is proportional to the level of injury and diminishes with time.

Seizures in aviators are of obvious concern because of the almost certain risk of injury to self or others. Although partial seizures are not fully incapacitating as Grand Mal (generalized) seizures, they can interfere with critical tasks and have the potential to secondarily become generalized. Seizures are more likely following sleep deprivation, heavy alcohol use, illicit drug use, severe head trauma, brain infections bleeding or tumors. Post-ictal confusion following a seizure helps to distinguish it from syncope.

Syncope is most often caused by vasodepressor (vasovagal), neurogenic, orthostatic, and cardiac etiologies. Transient loss of consciousness from a two-thirds reduction or more of cerebral blood flow differs from seizure in several ways. The rapid return to normal level of attentiveness, facial pallor and sweating, occurring only in upright posture or precipitated by anxiety or pain (e.g. venipuncture) are typical features of syncope. Lightheadedness, with loss of peripheral vision "graying out" and unconsciousness can occur during flight when blood flow to the brain is reduced by "G" forces (G-LOC). Typical features of seizure include focal sensory or motor phenomena, auras, bladder incontinence, tongue or cheek bites, muscle soreness, lethargy and unnatural need to sleep, headache and post-episode (post-ictal) confusion. Correct diagnosis of loss of consciousness is essential and aviators are grounded until the diagnosis is clear and is not likely to recur.

Convulsive Syncope may be confused with seizure and may be experienced in 12% of syncope cases. The convulsive movements are identical to those seen in seizure but are due to more severe or prolonged diminution of blood flow to the brain. This is most often seen when a person is maintained in the upright or sitting position following syncope in an attempt to prevent injury. Falling to the ground serves an important compensatory role in syncope.

Hypoxia in the aviation environment can result in loss of consciousness. Typical symptoms include decrease in night vision, drowsiness, air hunger, apprehension, fatigue, nausea, headache, dizziness, hot and cold flashes, euphoria, blurred vision, tunnel vision, numbness, tingling, poor judgment and coordination, difficulty talking, unconsciousness, convulsions, circulatory failure and in the critical stage, death.

Hyperventilation causes in increase in blood pH, vasoconstriction of blood vessels supplying the brain, resulting in a drop in the oxygen concentration and unconsciousness if severe enough.

Excessive Daytime Sleepiness (EDS) is a symptom common to several sleep disorders. It is also a common complaint during sustained flight operations and is due to inadequate restorative sleep. Regardless of the cause, EDS can result in mishaps from fatigue, poor concentration, inattention or inadvertently falling asleep. Sleep disorders associated with EDS are Sleep Apnea Syndrome, Narcolepsy, Periodic Movements of Sleep, and Restless Legs Syndrome. An overnight polysomnogram and multiple sleep latency test aid in the diagnosis of these sleep disorders.

Toxin exposure from environmental hazards in the aviation environment can result in confusion, delirium, delusions, coma and death. Organic hydrocarbons (jet fuel), solvents, carbon monoxide and other combustion products are common toxins. Others include alcohol, drugs, medications, heavy metals, food poisoning, and organophosphates (insecticides, nerve agents).

Heat exhaustion results from excessive sweating without fluid replacement causing fatigue, weakness and anxiety. The individual has cold, pale, clammy skin and disordered mentation with a slow pulse and low blood pressure. Heatstroke differs in that the skin is hot, flushed and usually dry with a rapid pulse and no drop in blood pressure. Disorientation may briefly precede unconsciousness or convulsions, the temperature climbs rapidly to 40º C (104º F) or higher and is a medical emergency.

Acute infections such as meningitis, septicemia and toxic shock can cause mental confusion and are medical emergencies.

This section was contributed by CDR Henry Porter, MC, USN (FS). 

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