DUA

10 2. ere

ACKNOWLEDGMENT

The authors wish to express their apprecia-
tion for the assistance offered by C, G, Gunn,
M. D., Associate Professor of Medicine, Uni-
versity of Oklahoma Medical School, who per-
formed the neurological consultation; William
E. Collins, Ph. D., Psychology Branch, CARI,
who performed the vestibular function tests;
Francis J. Nagle, Ph. D., Biodynamics Evalua-
tion Section, CARI, who performed the cardio-
respiratory evaluation test; Mr. A, Howard
Hasbrook, Chief, Crash Safety Section, CARI,
who conducted the flight test; Miss Patricia
Korty, Pharmacology-Biochemistry Branch,
CARI, who performed the blood glucose deter-
minations; and Mr. Alvin L, Armstrong who
recorded the electroencephalograms,


Co

eo-



Other causes of vertigo have been considered
but none was confirmed by our findings, Sud-
den alteration of the air pressure in the middle
ear can cause acute transient attacks of vertigo
in airmen but should not occur between ground
level and 400 feet during ascent. Endolym-
phatic hydrops is common and is a leading
cause of abrupt attacks of vertigo lasting min-
utes or hours. Absent in this case, however,
were the commonly associated stress, endocrine
imbalance, tinnitus, hearing loss, reduced re-
sponse to caloric test, sensation of aural pres-
sure, nausea, and vomiting, A vasomotor dis-
turbance involving endarterial branch vessels
of the labyrinthine artery can cause postural
vertigo and similar involvement of other vessels
could explain the prolonged period of uncon-
sciousness, but there is no family history, re-
ported stress or recurrence to support this
explanation.

Duration of the vertigo was inadequate for
an acute toxic labyrinthitis or for a vestibular
neuronitis. Because of the EEG abnormalities,
consideration was given to disorders of the
cerebellum, cerebral cortex and eighth nerve
which can cause vertigo but there was no
conclusive evidence to support a diagnosis
of involvement of any of these areas,

The history of an allergy, the associated gas-
trointestinal symptoms, and the acoustic dip
at 4000 and 6000 cps are not unusual findings
in airmen with vertigo but, unfortunately, they
do not help establish a diagnosis in this case.

While incapacitation occurs with severe ver-
tigo, associated loss of consciousness, which
occurred here, is seldom reported. 7

Despite the absence of any external markings
about the head, head impact’ during the crash
must be seriously considerel as the cause of
prolonging the unconsciousness to almost two
hours, His position at the time of discovery
suggests that the seat belt) was never fastened,
that his head impacted soft ground duping the
crash, and that recovery from syncope would
have been prompt in his head-down position.

During the EEG tests, various activating

ethods were employed to provoke syncope or
seizure attack. As the subject was sensitive
to bright light, Photostimulation with a moder-
ate intensity was attempted, His EEG showed
synchronization to all the test frequencies (3,
5, 7, 10, 20, and 30 per second), indicating

—~9—

sensitivity to photostimulation. However, no
epileptic discharge was observed. His response
to photostimulation probably cannot be con-
sidered abnormal as Pantelakis et. al." showed
that photostimulation produced epileptic EEG
discharges in 13 out of 14 photo-sensitive chil-
dren. Nor can the appearance of positive
spikes from the occipital region (lambda waves)
during photostimulation be considered abnor-
mal as most normal persons show lambda waves
in response to photostimulation under certain
conditions,’*"*

Other activating methods failing to provoke
EEG abnormalities are the tilt table orthostatic
tolerance test used by Dermksian and Lamb,'*
the valsalva maneuver used by Duvoisin et al.,
and the 10 second ocular compression method
used by Gastaut and his colleagues.** Hyper-
ventilation for three minutes did produce high
voltage slow waves but except on one occasion
the abnormal waves subsided within one min-
ute, Although hyperventilation is routinely
used clinically for EEG activation, its value for
diagnosis is always questionable, Balke et al."
showed that the response to hypocapnia can
be modified by training or acclimatization,

Seipel and Wentz” observed aggravated ab-
normal waves on their subject at the fourth and
fifth hour of the glucose tolerance test when
the blood sugar level was 65 and 80 mg, per
cent. In our case, no aggravated abnormal
waves were observed during the entire five
hours of glucose tolerance test although the
blood sugar level reached 73, 43, and 51 mg, per
cent at the third, fourth, and fifth hour after the
ingestion of 100 g. of glucose.

The only positive findings in our study are
the presencé of 5-7 per second theta waves in
his resting EEG records and the appearance of
high voltage slow waves during irrigation of his
right ear. His resting theta waves were of
moderate amplitude (50-100 #V) and often
nearly sinusoidal in shape. Cobb” considered
that monorhythmicity, ie, simple sinusoidal
waves not mixed with other frequencies, is
more significant than mixed waves, Most in-
vestigators”TM consider bilateral theta as an in-
dication of lesions involving various subcortical
areas including thalamus, hypothalamus, mid-
brain, pons or medulla. One author,* however,
considered mid-line theta discharge as an indi-
cation of temporal lobe epilepsy. According to



Tigure 6. Photostimulation at 7 per second frequency. Stimulations marked by spikes in

lead C,. EEG synchronization best seen im 0, lead. Lambda waves in 0, lead. a ry

Fer -Ay

Fra-Ae

T3-Ay

Ta Aa

-~6—



Figure 5. Topographical distribution of theta waves (stippled area).

as shown by the stippled area, This area is bilaterally
situated and includes the midline leads F, and C,, Fron-
tally the prominent area is more or less restricted to the
medial portion of the cortex and caudally it spreads more
laterally to the posterial parietal ( P, and P,) and temporal
(T, and T,) areas,

Flashes of 10 microseconds duration and approximately
50,000 candle power peak intensity at the eye level were
provided with a Grass PS 2 Photostimulator. Frequencies
of 3, 5, 7, 10, 20 and 30 per second were employed. On
all three examinations (June 5 and August 7,, 1062, and
January 29, 1963) the subject, with eyes open, responded
to all these frequencies with occipital lead synchronization.
However, only occasional synchronieations were observed
on 3, 20 and 30 per second stimyfations. More faithful
and prominent waves followed the 3, 7, and 10 per second
stimulations, Figure 6 shows an EEG record taken on the
second examination during photostimulation at the fre-

uency of 7 per second. The flashes are marked /by the
sharp ‘spikes in lead C, and synchronization is besf/seen in
lead 0, The positive spikes shown in lead 0, ard presum-
ably the lambda waves which occur in normal individuals
when. the illumination is strong and the subject gazes at
the light with intention.2"* Our subject showed these
waves in 0, lead in both the later examinations but not in
the first one. Although the subject responded to photo-

mulation with faithful synchronization of occipital waves,
there were neither gbnormal waves or spikes, nor the ap-
pearance of seizure-like motor responses. Synchronization
was limited to occipital leads and seldom spread to the
C, and C, leads. Even with higher intensity of stimulation
‘(2x and 4x), no abnormal brain waves or movements were
observed.

~5-

In all three examinations, the subject was instructed to
breathe as deeply as he could for 3 minutes and to keep
each inspiration and expiration with the beats of an elec-
tric metronome which was set at the rate of 80 per minute.
High voltage slow waves appeared in the Fr, Fr,, Cy C,,
0,, and 0, leads and sometimes in the T, and T, leads dur-
ing hyperventilation (Fig. 7). Return of brain waves to
his resting level occurred within one minute in the first and
third examinations. In the second examination, high volt-
age slow waves persisted until 160 seconds after cessation
of hyperventilation. Valsalva and breath-holding also pto-
duced no significant EEG changes.

In the third examination external auditory canal irriga-
tion for 30 secends with water at 25°C was performed on
the subject while he was lying supine with his head tilted
to tne side, Electroencephalograms from Fe, Fe, T,, Ty,
C,, C,, and 0, were recorded on seven channels and, on
the last channel, horizontal movements of the left eye were
recorded with twingsilver-disc electrodes, one close to the
lateral canthus and the other on the bridge of the nose.
Three .irrigations were performed, the first two on the left
side and the last one on the right side. In the first test,
nystagmic eye movements with the fast component towards
the right side started 38 seconds following the beginning of
left canal irrigation. The maximum amplitude of the elec-
trical signal was about 250 xV and the frequency of the
nystagmus was’ from 2-3 per second. The duration of
high amplitude nystagmus was only 5 seconds. The ampli-
tude of the remaining nystagmus potential was below 100
2V. The total duration of discernable nystagmus (above
50uV) was 110 seconds. In the second test, the left ear
was irrigated again while the subject performed an arith-
metic task. The result was comparable to the first except



Figure 9. High voltage slow waves in all EEG leads 108 seconds after irrigation of right
ear. Bottom channel shows the record of nystagmic eye movements.

—~8-



: INFLIGHT LOSS OF CONSCIOUSNESS
{ _ A CASE REPORT

PEI CHIN TANG, Ph. D.
Chief, Neurophysiology Branch

J. ROBERT DILLE, M.D.
Program Advisory Officer

E.R.A.U. LIBRARY

FEDERAL AVIATION AGENCY

Doc _ AVIATION MEDICAL SERVICE
FAA : AEROMEDICAL RESEARCH DIVISION
AM CIVIL AEROMEDICAL RESEARCH INSTITUTE

63 OKLAHOMA CITY, OKLAHt
21 .

A



sud-

10.

ll.

REFERENCES

DERMKSIAN, G., and L, E. LAMB, Syn-
cope in population of healthy young adults.
J.A.M.A, 168: 1200-1207, 1958,

DERMKSIAN, G., and L. E. LAMB.
Cardiac arrhythmias in experimental syn-
cope. J.A.M.A. 168: 1623-1630, 1958.

GASTAUT, H,, and M. FISCHER-
WILLIAMS, Electroencephalographic
study of syncope, its differentiation from
epilepsy. Lancet 7004: 1018-1025, 1957.

GASTAUT, H. Syncope and seizure, EEG
Clin. Neurophysiol. 10: 571-572, 1958,

GASTAUT, H., and C, GIBSON. Electro-
graphic study of syncopal predisposition.
Aerospace Medicine 31: 531-542, 1960.

DUVOISIN, R. C., F. KRUSE, JR., and D.
SAUNDERS. Convulsive syncope induced
by the valsalva maneuver in subjects ex-
hibiting low G tolerance. Aerospace Medi-
cine 33: 92-96, 1962.

SEM-JACOBSON, C. W., D. NILSENG,
C. PATTON, and O. ERIKSEN. EEG re-
cording in simulated combat flight in a
jet fighter plane, (EEG lab., Norway)
EEG Clin, Neurophysiol. 11: 154-155, 1959,

SEM-JACOBSEN, C. W. Electroencephal-
ographic study of pilot stresses in flight.
Aerospace Medicine 30: 797-801 1959,

GASTAUT, H., M. ©. LEE, and P.
LABOUREUR. Compprative EEG and
psychometric data for’ 825 French naval
pilots and 511 control subjects of the same
age. Aerospace Medicine 31: 547-552,
1960. ’ é

ADES, H. W. Electroencephalographic
findings in relation to episodes of altered

consciousness in aviators, Aerospace Medi-
cine 33: 263-274, 1962.

SEIPEL, ¥. H., and A. E, WENTZ, Un-
suspected neurologic disease in aviation

personnel: A, Survival following seizures
in flight — I. Aerospace Medicine 34:
552-555, 1963.

,

12,

13,

14.

15.

16.

17.

18.

19.

20.

21.

-li-

EVANS, C. C. Comments on occipital
sharp waves responsive to visual stimuli.
EEG Clin, Neurophysiol, 1: 111, 1959.

EVANS, C. C. Spontaneous excitation of
the visual cortex and association areas —
lambda waves. EEG Clin. Neurophysiol.
5: 69-74, 1953,

REMOND, A., and N. LESEVRE. The
conditions of appearance and the statistical
importance of the lambda waves in normal
subjects. EEG Clin. Neurophysiol. 8: 172,
1956.

GROETHUYSEN, U. C., and R. G. BICK-
FORD. Study of the lambda waves re-
sponse of human beings. EEG Clin, Neu-
rophysiol, 8: 344, 1956.

GREEN, J. Some observations on lambda
waves and peripheral stimulation. EEG
Clin, Neurophysiol. 9: 691-704, 1957.

PANTELAKIS, S. N., B. D. BOWER, and
H. D. JONES, Convulsions and television
viewing. British Medical Journal 2: 633-
638, 1962.

BALKE, B., J. P. ELLIS, JR, and J. G.
WELLS. Adaptive responses to hyper-
ventilation, J. Applied Physiol, 12: 269-
277, 1958.

COBB, W. A. Rhythmic slow discharges
in the electroencephalogram. J. Neurol.
Neurosurg. Psychiat. 8: 65-78, 1945,

COBB, «jv. A. Electroencephalographic
abnormaljties as signs of localized path-

“ology. EEG abnormalities at a distance

from the lesions. Quatrieme Congr, Intern.
Electroenceph. Neurophysiol. Clin., (Brux-
elles) pp. 205-223, 1957.

WALTER, W. G., and V. J. DOVEY.
Electro-encephalography in cases of sub-

cortical tumor. J. Neurel. Neurosurg.
Psychiat. 7: 57-65, 1944.



Cobb” and Walter and Dovey,” bilateral theta
is the most frequently encountered EEG ab-
normality, It is also interesting to note that
both our subject and the subject reported by
Seipel and Wentz showed this type of abnormal
waves, This leads to the question of whether
or not loss of consciousness may often be asso-
ciated with bilateral theta rhythm, Although
most studies were made on tumors, other causes
can also produce subcortical lesions. In our
case, we cannot rule out the possibility that
the abnormal EEG activity is the result of
traumatic head injury since the subject had
sustained head injury in his boyhood and also
might have had concussion during his crash
after landing. However, Cobb” found that
rhythmic EEG activity due to head injury
usually disappeared by the end of three weeks,
and our subject showed persistent bilateral
theta rhythm two, four and nine months after

the incident indicating that the rhythm is more |

likely a permanent feature and not the tempor-
ary effect of head trauma, The appearance of
high voltage slow waves during the caloric test
was unexpected. However, the fact that ab-

normal EEG waves can be provoked by ves- '

tibular stimulation appears to be in perfect

agreement with the contention that the lesion,
if there is any, must be subcortical and very
likely in the brain stem,

Recently Henry and HelferTM reported a case
of sudden complete incapacitation of an appar-
ently healthy ATR pilot. He was found to have
a constricted middle cerebral artery on the right
side as revealed by arteriogram. The authors
raised the question of whether the existence of
the lesion should have been detected during
one of the 15 physical examinations made dur-
ing six years preceding the episode. If an elec-
troencephalogram had been performed during
a physical examination of their pilot, it could
have led to diagnostic studies before his sud-
den incapacitation,

Because of the possibility of unpredictable

[ recurrences with serious consequences, it would

be hazardous for this airman to resume flying
\ until the cause (or causes) and relationship of
his vertigo, period of unconsciousness, and EEG

‘abnormality are better understood, Pursuit

of a career in commercial aviation would be
particularly unwise at this time. Periodic as-
sessments of his interval history and physical
condition are planned to determine when, or if,
he may safely return to flying,


that the duration of high amplitude nystagmus was pro-
longed to about 100 seconds with a total duration of dis-
cernable nystagmus of more than 200 seconds No other
abnormal brain waves were noted in these two tests except
some 5-7 per second waves similar to those appearing in
his resting records. The subject reported that he experi-
enced no unusual sensations or discomfort during these
tests. The subject was then allowed to rest for more than
10 minutes with periodic EEG recordings made during the
iod. A large number of theta waves appeared dur-
period, much more frequently than in his previous
resting records.

In the third test, the right ear was irrigated with the
same procedure. High amplitude nystagmus (about 210
#V) with 2-3 per second frequency appeared 40 seconds
after the start of irrigation. However, this high amplitude
nystagmus lasted for more than 200 seconds. At about 43
seconds after the onset of nystagmus, high voltage slow
waves (2-3 and 4-5 per second) appeared in, all the re-
corded leads and lasted 46 seconds (Figs. 8 and 9). These
waves are not unlike those appearing at the end of 3
minute hyperventilation (Fig. 7). Although some of the
slow waves appear to be synchronous with the nystagmic
eye movements (Fig. 8), suggesting that they could be the
result of artifacts, the facts that (1) these slow waves did
not appear after left ear irrigation which produced similar
amplitude and frequency of nystagmus, (2) they did not
appear in the rest of the over 200 second records after
right ear irrigation with the same amount of nystagmus
present, and (3) many slow waves (Figs. 8 and 9) did
not appear to be synchronous with the eye movements,
indicate that these slow waves probably were true synchro-
nized discharges from the cortex. #The subject reported
that during this last test he experienced the same sensation
of light-headedness and dizziness as he did just prior to
his loss of consciousness in the airplane.

TABLE I
’ Heart Rate
Position per minute
Supine 58!
60° feet down ‘ 69
Ist minute ; 69
2nd minute _ , 69
3rd minute , 74 /
4th minute 6B /
5th minute 7
6th minute 70 .
e 7th minute val
8th minut 1
9th minute 68
. 10th minute 64
11th minute 7

-7-

The subject was placed on a tilt table and an EEG. was
recorded from the Fr,, Fr,, T,, T,, C,, C,, and 0, leads in
the top seven channels of the electroencephalograph. The
last channel recorded the subject’s ECG from his two arms.
His heart rates before and during the 10 minute 60° feet
down tilt from a supine position are shown in Table 1.
No cardiac arrhythmia was noted during this period and the
subject reported no unusual feelings, At the end of the
tenth minute, firm pressure was applied to his eyes with
thumbs for fifteen seconds, His heart rate at the end of
ocular compression was 65 per minute and again no cardiac
arthythmia was noted. The patient again reported no un-
usual feelings, At the end of the eleventh minute, the
heart rate was 71 per minute and the subject was tilted
back to his supine position.

Electroencephalogram was periodically recorded at half
hour intervals throughout five hour glucose tolerance test.
No abnormal waves other than his usual theta waves were
observed throughout the test even though at one time his
blood glucose was as low as 43 mg/100 ce.

DISCUSSION

The occurrence in this case of inflight true
vertigo followed by almost two hours of un-

. consciousness presents a most difficult diagnos-.

tic problem; one that is not yet completely
resolved,

A great deal of interest exists in the field
of aviation medicine in the vertiginous effect
of flicker produced by light passing intermit-
tently through rotating helicopter blades, Sim-
ilar effects may be noted by pilots who view
the sun through propellers, or see sunlight
reflected off the propellers, of aircraft, partic-
ularly single engine models with tandem seat-
ing. Despite the possiblity of appropriate flight
conditions and the EEG finding of photic
synchronization, flicker vertigo and a grand
mal seizure can probably be ruled out in this
case by the absence of subjective discomfort
during photostimulation and the absence of
epileptic EEG discharges even during photo-
stiraulation.

The spontaneous statement by this airman
that the sensory experience with caloric stim-
ulation was id@fitical to that of the original
episode confirms our suspicion that true ves-
tibular vertigo occurred. ; The vertigo pro-
duced during the examination by the caloric

, test and by rotation in a Barany turning chair

was a normal physiologic response of the laby-
rinth, While considerable motion of the head °
preceded the initial episode of vertigo, neither
the flight path of the aircraft nor the reported
subjective sensations are consistent with Coriolis
reaction.



nose-up
than 60°)

slightly Figure 1. International nomenclature for EEG electrode positions.

Foi -Ay
Fra-Ap

T3-Ay

Ta-Ae

C3 -Ay

Gq -Ag|

O1,-Ay

Figure 2, Resting EEG showing the nearly sinusoidal theta waves, more prominent in Fr,,
s.

» C, and C, lead

3+


did not seem unusually fast or slow. There were no signs
of injury but an ambulance was called.

He regained consciousness in the ambulance approxi-
mately two hours after the onset of unconsciousness. He
had no vertigo, only a cold sensation of the nose and throat.
(He was receiving 0, by mask at the time.) The ambulance
attendant noted the odor of vomitus but found no evidence
of it.

He was taken to the emergency room of a local hospital
where a B.P. of 160/70 and extreme nervousness were the
only recorded findings, He received intramuscular injec-
tions of promethazine HC1, 50 mg., and meperidine HCl,
50 mg. He slept from 3:00 p.m., April 13, to 9:00 a.m.,
April 14, awaking with thirst, anorexia, nausea, and a
headache (dull, bilateral, frontal without throbbing) which
persisted until 5:00 pm, that day. Symptoms remitted
spontaneously and he has been asymptomatic to the present.

There is no evidence to support the statement by the
attending physician that the airman had an upper respira-
tory infection with a middle ear obstruction creating diz~
ziness and the black-out. The attending physician reported
that symptoms cleared after antibiotic petapy which the
patient denies receiving.

Past medical history reveals a brief loss of consciousness
at age 10 due to trauma from a baseball bat, occasional ex-
ternal ear infections in the summer, and the usual child-
hood diseases without complications.

The family history is non-contributory.

The review of systems revealed only rare faint sensa-
tions on sudden change of position, an allergy to penicillin,
Spectacle correction of myopia with tinted lenses due to
“hypersensitivity to light,” mild dissatisfaction with present
duties (part-time retail store assistant manager), occasional
mild depression, and occasional fatigue upon awakening.

On physical examination on June 4, 1962, the airman
weighed 113 pounds and was 64 1/2 inches tall, Distant
vision was 20/40 in each eye with spectacle correction to
20/15 O.D, and 20/20 O.S. There was a 50 db loss in
hearing by air conduction at 4000 and 6000 cps, A.S. and
6000 cps, A.D. determined by pure tone audiometry. The
blood pressure was 104/50, recumbent. The resting pulse
was 60 per minute which returned to 76 per minute after
exercise. During an orthostatic tolerance test the blood
pressure was 120/72 and the pulse rate 90 per minute after
-standing for three minutes. Bilateral caloric stimulation
for 40 seconds with 28°C water produced strong nystagmus
and dizziness with recovery in five minutes. Head move-
ment during rotation produced symptoms of similar in-
tensity and duration. The remainder of the examination,
inclu ing the neurological examination, jvas within normal
limits, '

A neurological consultation was obtained on August 7,
1962, and no evidence of neurologica} disease was found.

Laboratory studies performed on June 5, 1962, were’ as
follows: red blood count, 5,090,000 'per cubic milliméter;
hematocrit, 49 per cent; hemoglobin, 16.3 gm, erytfocyte
sedimentation rate, 3 mm. per hour; white ‘blood’ count,
9,600 with normal differential; fasting glucose, 99 mg.%;

two hour post-prandial glucose, 104 mg. %; and urinalysis, ,

normal. During a five hour oral glucose tolerance test,
pew>rmed on January 29, 1963, blood glucose levels were:
fasting, 102 rg.&; 30 rpin., 135 mg.%; 1 hr., 99 mg.%; 2 hr.,
105 mg.%; 3 hr, 73 ; 4 hr, 43 mg%; and 5 hr., 51
mg.%.

Radiographs of the skull and chest revealed no abnor-

malities. .

& — Electrocardiographie studies during resting and working
conditions were within normal limits.

During a cardio-respiratory evaluation test the resting
blood pressure was 112/70; the pulse rate, 70 per minute;
the maximum working blood pressure, 168/60 with a pulse
rate of 180 per minute; and the maximum oxygen intake
was 41.3 ml/kg /min. Passive tilting to 60° resulted in a
minimum blood pressure of 96/80 with a pulse rate of 96
per minute. There was no indication of any tendency for
orthostatic syncope.

On June 4, 1962, a flight test was given in a Cessna 172
by an instructor pilot accompanied by a flight surgeon.
He was subjected to the following maneuvers without any
admitted symptoms, pallor, sweating, or nystagmus: e-
peated duplications of the flight profile which preceded his
onset of vertigo and unconsciousness; vertical reversements
involving banks in both directions of approximately 90°
with maximum pitch-up angles of 45°; lazy 8 maneuvers
continuously for 4-5 minutes with speed changes from 70 to
120 mph, with roll angles and banks of 90° and nose-up
angles of 40-50°; and tight, steep turns (greater than 60°)
with ay ximately 2 £ for 2-3 minutes.

In the morning of June 5, 1962, an electroencephalo-
gram was recorded, Disc electrodes were placed at FP,,
Fr, F,, F,, C, C, Ty Ty 0, and 0,. Clip-on dise elec-
trodes were attached to the two ear lobes (A, and A,).
Fig. 1 shows the international nomenclature for the positions
of the EEG electrodes. A, was used as reference electrode
for all the left side electrodes and A, for right side elec-
trodes. The subject was instructed to relax in a supine
position in a semi-dark room. Recording was made with
a Grass Model III electroencephalograph.

His resting record showed high amplitude occipital alpha
waves, often above 100 uV and sometimes above 200 nV.
The left occipital alpha waves (0,—A,) were often slightly
suppressed. A slight suppression was also noted on the
right temporal records. However, the most significant find-
ing was the appearance of theta waves (5-6 per sec.)
shown in the Fr, and Fp, leads, often between 50 and 100
#V but sometimes above 100 «V. Less prominent theta
waves were also noted in the C, and C, leads. These theta
waves appeared while the subject was awake as indicated
by the presence of continuous alpha waves. These abnor-
mal waves appeared more often just before the subject
became drowsy. However, when the subject was drowsy
or asleep, theta waves were not observed.

The subject retumed on August 7 (about four months
after the accident) for a second study, The theta waves
in the Fr, Fr, C,.and C, leads persisted and occasionally
even appeared in the T,, T,, 0,, and 0, leads (Fig. 2). To
determine the relative prominence of these waves-on the
sealp, the zero leads were employed. Figure 3 shows the
appearance of prominent theta waves in F, and C, leads,
using A, and A, as niggeence leads. Less prominent theta
waves appeared in P, leads and almost none in occipital
leads, indifeating the more prominent frontal distribution of
these waves.

To complete the study of geometrical distribution of the
theta waves on the scalp, an EEG was recorded from F,,
¥,, F, F, P,, P,, T,, and T, leads. The records are shown
in Fig. 4. Theta waves appeared more prominently in leads

P,, T, and T, and slightly less in F, and F,.
There is some asymmetry in the prominence of the theta
waves, the left side being more prominent.

A topographical: distribution of the theta waves on the
scalp is shown in Fig. 5. The area of more prominent
theta waves is formed by linking the more prominent leads

-2-

oe



INFLIGHT LOSS OF CONSCIOUSNESS
A CASE REPORT

PEI CHIN TANG, Ph. D.
J. ROBERT DILLE, M.D.

ABSTRACT

A case of inflight vertigo and loss of consciousness in a private pilot, flying alone, is
presented. The differential diagnosis and the significance of the findings of 5-7 per second
theta waves in his resting EEG and high voltage slow waves during caloric irrigation of his
tight ear are discussed.

Loss of consciousness can result in serious con- __ started the engine and taxied out for take-off. At this
sequences when it involves a pilot in control of time he was wearing tinted prescription spectacles and

. " " t . a sport shirt with the collar open, had, to the best of
an aircraft, It is a manifestation of a variety of his knoviledge, his seat belt fastened.

physiological and metabolic disorders.'“* Cardio- The take-off was made to the SE on runway 12 at about
1. dysfi ti h: 1 be d 11:00 am. under clear skies. During the take-off roll
vascular dysfunctions have long been under the aircraft yawed and he noted that he could not reach

suspicion as a main cause and a number of in- the rudder pedals, He therefore leaned forward to adjust

vestigations has been devoted to studying their __ the seat but continued the roll. This adjustment was com-
volation to lose of consciousmess.* Aer BS esemt _Pleted and a normal posture was assumed prior to lift-off
al s - Pp He climbed at an unknown rate to 400 feet where, with-

the condition of the ‘cardiovascular system of a out a stall, the nose dropped abruptly to the horizon, He
pilot is under close surveillance both in military checked the altimeter, found his altitude in the 390's,

ivil aviati i looked out ofthe window tn-the Let-and-back, then relaxed
and civil aviation. Thus, syncope due to serious” -r-ttas point he noted lightheadedness, a’ sensation of

cardiovascular disturbances has become a de- _ back and forth movement of the control panel, and blurred
creasing threat to aviation safety, On the other vision. There was no diplopia, tingling, nausea, or tin-

hand, loss of consciousness due to nervous dis- fight ch This Ieee followed by tru fis oe felt in level
orders is poorly understood and only recently —_ became quite anxious at this point and decided to land.
have some studies been devoted to sub- He made two 180° tums and trimmed up the aircraft for
‘ectTM To ilk he i Fe this {mst approach. His vertigo was gradually intensifying dur-
ject. ‘0 illustrate the importance jof ising this period. .When about 10-12 feet off the ground, he

etiology an unusual case is reported. reached to his left with his right hand (without turning his
i head) to cut the*magneto switch. He remembers nothing
REPORT OF THE!CASE else until two hours later when he was in an ambulance,

recei¥ing oxygen, en route to the local hospital. During
this 2 hour period he remembers only a jolt.

A 19 year old student,pilot with aspirations of becoming
a commercial pilot, and 105 hours of flying time,) was The plane, at half throttle, landed level according to

completely asymptomatic until 11:00 am., April 19,/1962, Skid marks, then lefg.the ground and turned 180° stricking

etely c 0 fence at the end of the runway with the left wing an
it which time he ced vertigo and t loss 4 P y B
of consciousness; go subsequent then the, ground with the right wing. The landing gear

‘The evening before, being a “school night,” was quiet 88 tom off, the cowling damaged and the tail was bent.

i F t i i: There were no witnesses to the accident. He was first
Ticectons, He did note tone. Colgate uneasiness with, missed after he failed to land at the end of one-half hour

sausea before rotising, He ales well, ar wand, from’ ,a0¢ the plane was first sighted 1 1/4 hours after the
. 5 H baci .

00 pm to 6:55 am ste a usual bretkfast of bacon ee frst person on the scene, his instructor pilot, found

eggs, and coffee piten ce comege Casss “rom him lying on soft ground with his feet still in the aircraft,

8:00 a.m, to 10:50 Wen. There were no stressful events sppcaring only asleep. The seat belt was open, not broken,

The bridg

associated with these classes, in fact an exam was re- fe of his glasses was broken. ‘There was no pal-

tumed on which he made a better-than-expected grade, Jor sweating vomitus, incontinence, or body movement
He denies taking any drugs during this time. (twitching or jerking)” Respiration was described as slow

From school he drove immediately to the local airport, and regular without associated sounds. The pulse was felt
rented an Aeronca Champion which had recently landed, and described as strong. The rate was not counted but it

-1-



22. FAURE, J., J. DROOGLEEVER-

23.

FORTUYN, H. GASTAUT, L. LARRA-
MENDI, P. MARTIN, P. PASSOUANT, A,
REMOND, J. TITECA, and W. G. WAL-
TER. De la genese et de la signification
des rhythmes recueillis a distance dans les
cas de tumeurs cerebrales. EEG Clin.
Neurophysiol, 3: 429-434, 1951.

JASPER, H., and J. VAN BUREN. Inter-
relationship between cortex and subcortical
structures: Clinical electroencephalographic
studies, EEG Glin, Neurophysiol. Suppl. 4,
168-188, 1953.

FAA
AM
63-21

. SMALL, J. G., B. K. A. BAGCHI, and K.

A. KOOL. Electro-clinical profile of 117
deep cerebral tumors. EEG Clin. Neuro-
physiol, 13: 193-207, 1961.

. CIGANEK, L, Theta-discharges in the

middle line — EEG symptom of temporal
lobe epilepsy. EEG Clin. Neurophysiol.
13: 669-673, 1961.

. HENRY, C. D., and L. M. HELFER. Sud-

den complete incapacitation of an appar-
ently healthy ATR pilot. Aerospace Medi-
cine 34: 360-361, 1963.

Inflight loss.of congcious=<

ness a case report

DATE DUE