1Topic 3.6 Neurology AVMO 0017 study card

• • The impact of the condition on the operating environment
• • The impact of the aviation environment on the condition
• • Immediate fitness to fly
• • Outline what clinical information is required, including investigations and referrals, for determination of aeromedical disposition.
• • Describe the aeromedical implications of possible treatments for neurological disorders.
• • Discuss prognostic considerations that may impact on future fitness.
• • Propose a likely MECR process and aeromedical disposition for neurological disorders.
• • Apply an evidence-based aeromedical decision making framework to the aeromedical management of disorders affecting the nervous system.

• • Subarachnoid Haemorrhage
• • Syncope
• • Headache

• Clinical Condition
• Likelihood of clinical event:
• •Incidence and prevalence data
• •Prognostic factors
• •Risk factors
• •Effectiveness of Rx
• Determined from:
• •Investigations

• •Muticrew only
• •As-or-with co-pilot
• •Type restrictions
• •Area restrictions

• • Relatively common
• • Higher incidence among young adults, often in association with alcohol excess
• • Many and varied classification schemes depending on any or all of the following:
• • GCS, Duration of LOC/PTA, Radiographic changes on structural brain imaging
• • NB. Inconsistent approach to classification within various ADF policy documents

• • Will the condition impact on the aviation environment/operation (functional ability/incapacitating)?
• • Potentially yes
• • Primary aeromedical concerns following TBI are:
• • Post-Traumatic Epilepsy (PTE)
• • Neuropsychological impairment
• • Persisting neurological deficit
• • Will the aviation environment impact the condition?
• • Potentially yes.
• • Hypoxia, +Gz, mental and physical stress, circadian disruption, ?flicker/strobe effect
• Aeromedical Guide to Grading TBI…..

• CT/MRI Normal
• Non-displaced skull fracture
• MRI evidence of DAI
• or haemosiderin plugs
• Cerebral contusion

Penetrating injury

• • Detailed eyewitness account of nature of head injury and immediate sequelae is desirable
• • Mechanism of injury
• • Duration of LOC
• • Immediate vs delayed seizure activity
• • Ambulance and hospital records
• • Duration of PTA (be careful of confounding due to period of normal sleep and/or alcohol)

• • MRI or CT brain and skull
• • Neurological/Neurosurgical reports
• • Neuropsychological assessment
• • Sleep deprived EEG

• • An “iron-driven” phenomenon
• • Any intra-cerebral haemorrhage or contusion is considered aeromedically significant
• • Immediate seizure within 24hrs of injury not predictive of future risk of PTE in isolation to other findings
• • Duration of PTA >24hrs as independent predictor
• • Risk of PTE >30% in severe TBI
• • Risk of PTE declines with time
• • 27% have occurred by 3/12; 56% by 12/12; 70% by 24/12
• • can remain elevated beyond background population risk levels for more than 5-7 years

• • Will treatment of the condition impact on function in an aviation environment?
• • Use of prophylactic anticonvulsants not acceptable in civil or military aviation environments
• • Underlying risk of seizure for which Rx has been prescribed
• • Adverse effect of medication on cognition and alertness
• • Risk of withdrawal seizure upon abrupt discontinuation

• • All existing large prognostic studies for PTE are based on CT brain findings
• • Is use of modern high-resolution CT scanning and MRI leading to over-estimation of severity of TBI and PTE risk?
• • Significance of subtle impairment on neuropsychological assessment often difficult to interpret in the absence of reliable baseline data for comparison
• • An EEG will invariably be performed by Neurologist but realistically is of limited value due to high false-positive and false-negative rates

• • Is TMUFF required?
• • Yes – minimum 1 month TMUFF following mild head injury
• • Permanent disqualification to be anticipated following severe head injury
• • Recruits vs. trained aircrew
• • Case by case determination for history of mild and moderate head injuries in applicants. Severe head injuries typically permanently disqualifying for all ADF entry.
• • Health Directives or other references
• • HD293 not to be applied for resumption of flying duties in injured aircrew
• • Likely UAMECR/IAMECR/CAMECR outcome
• • Case by case determination for moderate (6-24/12) and severe (2-5 yrs) head injury

• • Trained Navy Pilot
• • Fell from mountain bike wearing a helmet
• • striking head on tree stump
• • 1 min LOC, 25-35mins PTA
• • CT head normal
• • However, MRI head abnormal
• • 8mm haemorrhagic lesion
• • MRI head abnormal
• • 8mm haemhorragic lesion
• • No change on repeat MRI/MRA after 2months
• • Normal sleep deprived EEG
• • Neurologist states no reason “incidentaloma” should cause pilot to remain grounded (at 3mths)
• • Awaiting neuropsychological report
• • Classify as Mild or Moderate Head injury?

• Condition Overview
• • Most commonly caused by rupture of cerebral aneurysms or arterio-venous malformation (AVM)
• • 15% of cases of acute SAH have no detectable source of bleed
• • Most common idiopathic source is perimesencephalic bleed (PM-SAH)

• Aeromedical Concerns
• • Will the condition impact on the aviation environment/operation (functional ability/incapacitating)? Yes
• • High mortality rate (50%)
• • High recurrence rate
• • 30% risk of re-bleed of aneurysmal SAH in first month and lifelong 2-3% annual risk
• • High chronic morbidity rate with neurological deficit and/or neuropsychological impairment
• • Increased risk of seizure following SAH
• • Vasospasm-induced ischaemic necrosis
• • Aneurysmal bleeding into neo-cortex
• • Iatrogenic risk following surgical intervention
• • NB: Much better outcomes with PM-SAH bleed
• • No increased mortality or morbidity
• • No increased risk of re-bleed
• • Will the aviation environment impact the condition?
• • ?Effect of physical and/or emotional stress increasing risk of re-bleed

• • CT/MRI imaging results
• • Source of bleed
• • MCA aneurysms are associated with higher incidence of subsequent seizure
• • Severity of bleed (Fisher Grade)
• • Better outcome for small bleeds detectable only on lumbar puncture (Fisher Grade 1)
• • Neurological/Neurosurgical opinion
• • Persisting neurological impairment
• • Neuropsychological testing
• • Risk factor management
• • Hypertension

• • Will treatment of the condition impact on function in an aviation environment?
• • Surgical clipping and/or cotton-wrapping of aneurysms is associated with higher incidence of subsequent seizure disorder compared with endovascular coiling
• • Use of prophylactic anticonvulsants not acceptable in civil or military aviation environments

• • PM-SAH may potentially be considered for return to flying duties
• • All other cases typically considered permanently disqualifying
• • Case by case determination

• • Syncope is a symptom rather than a diagnosis
• • Transient, self-limited LOC
• • Pre-syncope symptoms of hypo-perfusion such as faintness of tunneling of vision but nil LOC
• • History of the event is paramount in establishing an accurate differential diagnosis
• • Cause remains unknown in one third or more cases (Framingham Heart study)

• • Many and varied causes
• • Neurological
• • Cardiological
• • Gastrointestinal
• • ENT
• • Psychiatric
• • Physiological
• • Prolonged standing on parade
• • Dehydration
• • Heat syncope
• • G-LOC
• • Iatrogenic
• • Blood donation
• • Medication adverse effects

• • Will the condition impact on the aviation environment/operation (functional ability/incapacitating)?
• • Will the aviation environment impact the condition?
• • Hypoxia
• • +Gz exposure
• • Physical and emotional stress

• • Prodrome
• • Absent or present
• • Specific symptomatology
• • Posture at time of episode
• • Duration of episode
• • Activity immediately before episode and within 24hr period preceding episode

• • Head trauma
• • Post-ictal orientation
• • Urinary incontinence
• • Tongue-biting
• • Observer report
• • NB: Report of convulsive movements during episode is not diagnostic of seizure disorder
• • Bystander action

• • Frequency and pattern if recurrent episodes
• • Family history
• • Cardiovascular disease
• • Sudden death
• • Past medical history

• • Necessary further opinion and investigation may include
• • Neurological
• • EEG and MRI
• • Cardiological
• • Resting and orthostatic BP
• • 12-lead ECG
• • Holter monitor
• • EST
• • Echocardiogram
• • Tilt-table testing
• • ENT
• • Vestibular function testing

• • Will treatment of the condition impact on function in an aviation environment?
• • Treatment will depend on underlying cause
• • Any required treatment other than general advice to maintain fluid and electrolyte levels is to be considered disqualifying for military flying duties

• • TMUFF duration will vary depending on aetiology
• • Recruits vs. trained aircrew
• • Infrequent episodes of simple vaso-vagal syncope (due to explained cause such as venesection, pain, etc) is not disqualifying
• • Recurrent unexplained syncope is disqualifying for all entry
• • Health Directives or other references
• • Mandatory 72hrs TMUFF following blood donation for aircrew (24hrs TMUFF for ATC/JBAC)
• • Likely UAMECR/IAMECR/CAMECR outcome
• • Single episode of simple vaso-vagal syncope from explained cause does not warrant MECR
• • Case-by-case determination depending on aetiology for all other cases

• All cases assessed individually

• Nil specific further review other than monitoring of frequency of subsequent episodes

• Condition Overview
• • Lifetime prevalence of headache approaches 100%
• • Diverse spectrum of headache disorder ranging from simple muscular tension headache to classical migraine
• • Individual may experience more than one headache type
• • Genetic predisposition for migraine headaches
• • Headache may not necessarily be the most prominent or aeromedically important feature of migraine
• • Vestibular or Ocular migraine without headache

• • Will the condition impact on the aviation environment/operation (functional ability/incapacitating)?
• • Must consider the potential for sudden significant neurological symptoms such as loss of vision, photophobia, weakness, incoordination, and dysphasia
• • Nature of headache and associated symptoms are more important than formal headache diagnosis in determining aeromedical outcome
• • Will the aviation environment impact the condition?
• • Possible precipitation by altitude, glare, hot/cold extremes, dehydration, fatigue, circadian shift, and physical and/or emotional stress

• • Precipitating factors
• • Is trigger identifiable and avoidable?
• • Speed of onset
• • Is there any warning aura?
• • Period of prodrome
• • Seconds…minutes…hours
• • Frequency of attack
• • Isolated or recurrent
• • Clusters

• • Neurological symptoms
• • Aura (?incapacitating in own right)
• • Photophobia
• • Visual changes
• • Paraesthesia
• • Paralysis
• • Vestibular disturbance
• • Dysphasia

• • Severity of headache
• • Analgesic requirements
• • Bedrest requirements
• • Lost time from work
• • Treatment requirements
• • Prophylaxis not acceptable for military aviation

• • Objective investigations most commonly find no abnormality
• • Neurological opinion
• • MRI brain +/-MRA
• • Detailed history is essential to Neurologist in diagnosis of headache type, but symptom reporting usually most accurate at first presentation with treating doctor…

• • Requirement for headache prophylaxis disqualifying for military flying duties
• • Underlying medical condition is disqualifying
• • Adverse effects of some prophylactic medications (e.g. TCA, β-blockers) are disqualifying in own right

• • Period of observation required after first episode of severe headache
• • Permits Neurologist referral/investigation
• • Ascertain pattern of recurrence
• • Likely future disposition
• • Case by case determination
• • Nature and severity of headache and associated aura more important than diagnosis
• • More than 3 severe headaches per annum unlikely to be considered favourably
• • Avoidable trigger is beneficial
• • AVMED will consider need for restricted as-or-with aircrew duties

• • TMUFF - Minimum 3 months after first episode severe headache
• • Recruits vs. trained aircrew
• • Single episode of migraine within last 3 years is disqualifying for recruits
• • Any history of recurrent migraine is disqualifying
• • Infrequent uncomplicated mild headache that responds to simple analgesia can be considered fit
• • Nil specific further review other than monitoring of frequency of subsequent episodes

• TMUFF?
• Likelihood of clinical event:
• •Incidence and prevalence data
• •Prognostic factors
• •Risk factors
• •Effectiveness of Rx
• Determined from:
• •Investigations

• •Muticrew only
• •As-or-with co-pilot
• •Type restrictions
• •Referral Reports