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Abstract:
Head injury is responsible for development of auditory changes and deafness is a known sequelae to head injury.
The aim of this work is to study the incidence of the audiological disturbances in the immediate Post-injury period in patients with minor head injuries, to find out the frequency of such changes and to detect possible recovery during a three months observation period.
Different factors like age, sex, type and anatomical site of trauma, may influence the prognosis of auditory damage.
The study was conducted on fifty minor head injury patients seen in the Out Patient Dept of Hamad Hospital, Doha, Al Magribi Hospital, Jeddah, and Cairo University Hospital, Cairo.
A detailed history of the injuries were recorded including a full audiological and neurological history. Clinical otological examination was performed, pure tone audiogram, L.D.L., Acoustic impedance and brain stem audiometry were conducted. Data were collected analyzed and presented.
The results were statistically studied and revealed the involvement of 10 cases of hearing loss that mainly affected the high frequencies than low frequencies. We found that low frequency hearing loss patients recovered better than those with high frequency hearing loss. Vertigo and tinnitus were transient and disappeared spontaneously within the first week. We compared our findings with results of other authors and conclusions were suggested.
 Introduction:
Head injury is a common cause of mortality and morbidity. It is responsible for the development of auditory changes and deafness is a known sequel to head injury (1).
The commonest form of hearing loss is bilateral high frequency deficit(2), most profound around 4 kHz; recovery ma occur over the
first few weeks, ( 6) especially at 8 kHz, but
rarely complete(5). Closed head injuries may damage the vestibular cochlear system either in the peripheral labyrinth 0 in more central structures (2).
It is planned in this study to find out the incidence
of audiological abnormalities encountered following minor form
of head injury and to detect possible early recovery in the subsequent three months period.
Materials and Methods:
Fifty patients were included in this
study. Forty -eight male and 2 females,
with ages ranging between (12 -60) years.
All patients were examined within 3 days
of injury .
Cases were selected according to the selection
criteria in table (1) .The patients were
then subdivided into two group according
to the mechanism of injury.
Group I : Comprised of 36 patients who
sustained trauma to a moving head.
Group II: Comprised of 14 patients who
sustained trauma to a fixed head.
The control group was comprised of 20
healthy normal adults matched for age
and sex distribution of the patients,
with no history of ear diseases or history
of head injury.
The duration of post traumatic amnesia
was measured fro the time of injury to
restoration of full consciousness.
A total of 50 patients satisfied the inclusion
criteria for investigation. All patients
were examined within one to three days
from the injury. A detailed history of
injury was take together with a full audiological
and neurological examination. The mechanism
and anatomical site of head trauma and
duration of amnesia were recorded.
Signs of otitis media, fluid, blood, pus
in the ear and previous ear surgery were
excluded. Skull x-rays were done to exclude
fractures which, if present, the patient
was excluded from the study. Clinical neurological
evaluation including evaluation 0 the
cranial nerves, signs of lateralization,
signs of focal brain damage were recorded.
All patients had a pure tone audiometry,
using Amplaid 207 diagnostic audiometer
calibrated to internationally accepted
standards. Pure tone audiometry by air
conduction and by bone conduction at 250,
500, 1000, 2000, 4000, 8000 Hz was performed.
L.D.L. as well as acoustic impedance test
were done for all cases using Amplaid
728
Brain stem evoked potential audiometry
using Amplaid MK5 was used for all cases
to find out if there was central deafness
or not. All patients were interviewed
at three months and further audiological
measurements were performed.
Results:
This study was carried out on fifty patients
suffering from minor head injuries without
radiological evidence of skull fracture,
48 males and 2 females. Ages ranged from
12 to 60 years, thirty patients ( 60%
) were suffering from mild trauma to a
moving head with no audiological changes,
six patients (12%) were suffering from
mild trauma to a moving head with audiological
changes, ten cases (20% ) were suffering
from mild trauma to a fixed head with
no audiological changes, while four cases
(8%) were suffering from mild trauma to
a fIXed head with audiological changes.
Post' traumatic amnesia was less than
6 hours in all cases. (Amnesia was defined
as Total or partial loss of memory following
physical injury. In this study Antegrade
amnesia is loss of memory for events,
following some trauma is considered).
Twenty healthy persons were taken as control
group matched for, sex, and age group
of the patients.
1. Incidence of hearing loss:
Ten patients (20%) had sensorineural hearing
loss. Out of these cases, 8 of them (
80% ) presented with cochlear hearing
loss, 2 ( 20% ) presented with retrocochlear
hearing loss, but no central hearing loss
was observed. The high frequency loss
(4 & 8 kHz) was observed in most cases
(96%) and two cases (4%) where low frequency
loss (0.25 kHz) was noted.
2. Incidence of hearing loss in relation
to site of trauma: Temporal: In (19) patients
the trauma was directed to the temporal
region, five(26.3%) cases had sensorineural
hearing loss on the same side.
Occipital: In (11) patients the trauma
was directed to the occipital region but
only (3) cases (27.2%) suffered from sensorineural
hearing loss.
Frontal: Sixteen patients suffered from
trauma to the frontal region but only
(2) cases(12.5%) had sensorineural hearing
loss.
Vertical: In four patients the trauma
was directed to the vertex but no Sensorineural
hearing loss was observed.
3. Incidence of post traumatic amnesia
in relation to site of trauma:
In the post traumatic amnesia found in
all the cases of this study, there was
no statistical difference between the
duration of post-traumatic amnesia and
the duration of trauma.
4. Incidence of hearing loss in relation
to period of amnesia:
Mean duration of post -traumatic amnesia
was 1.19 hrs Ct 1.18) Mean duration of
sensorineural loss following amnesia was
2.58 hrs (:t1.58).
5. Incidence of hearing loss and head
position during trauma:
Thirty six cases (72%) received trauma
to a moving head, while 14 cases (28%)
received trauma to a fixed head. Out of
these cases who received trauma to a moving
head (6) cases suffered from S.N .H.L.,
and (4) cases out of those who received
trauma to a fixed head suffered from S.N.H.L.
There was no statistically significant
difference between the two.
6. Incidence of hearing loss and vertigo:
Among the ten patients who suffered from
S.N.H.L. after exposure to head trauma,
seven patients (70%) had vertiginous symptoms.
The other 3 patients (30%), were free.
Of the forty patients who were free of
S.N .H.I. only nine patients (22.5%) had
vertiginous symptoms, while the other
31 patients (77.5%) were free.
7. Incidence of hearing loss and tinnitus:
Among the ten patients who suffered from
S.N.H.I. after exposure to head trauma,
six patients (60%) had tinnitus, while
the other four patients (40%) were free.
Of the forty patients who were free of
S.N.H.I. , twenty patients (50%) had tinnitus,
and 20 patients (50%) were free.
8. Patients were divided according to
trauma whether to a moving head or fixed
head and audiological findings. Results
shown in tables (2A and 2B).
Results
of follow up:
Audiological measurements were performed
after 3 months to assess auditory functions.
All ten cases with S.N.H.L recovered within
three months.
As regards to vertigo, no patient sustained
vertigo for more than one or two days
after trauma, on the other hand, cases
with tinnitus disappeared within five
days from the injury .
Discussion:
Fifty cases of minor head injuries were
the subjects of the present study, 48
of them were males and only two were females.
Their ages ranged between (12 -60 years).
Age and sex distribution of cases in this
study showed a high incidence of S.N.H.L
in males, consistent with the previous
studies in the literature by (1).
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Selection Criteria:
(1) A history of post-traumatic
amnesia less than 6 hours.
(2) No radiological evidence of
fracture skull.
(3) Evidence of direct injury to
the skull.
(4) No evidence of previous ear
disease or trauma.
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Table (1) Selection
criteria
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Group I Trauma on
moving head
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Subgroup
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# of patients
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%
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Audiological findings
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A
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30
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60
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No Audiological Findings
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B
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4
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8
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Cochlear loss, low frequency SND
(250 Hz), good speech discrimination
,no tone decay, no delay in wave
(V) latency in BERA.
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C
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2
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4
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Retro- cochlear loss (high frequency
-4 & 8 kHz - poor speech discrimination,
positive tone decay and delayed
wave (V) latency on BERA.
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Table 2A : Incidence
of sensorineural hearing loss and
state of the head during trauma
(moving head).
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Group II Trauma on
moving head
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Subgroup
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# of patients
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%
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Audiological findings
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D
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10
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20
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No Audiological Findings
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E
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4
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8
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Cochlear loss ( high di frequency
SND -4 & 8 kHz) good speech discrimination,
no tone decay and no delay th in
wave (V) latency in BERA.
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Table 2 B Incidence
of sensorineural hearing lOss and
the state of head during trauma
(trauma on fixed head)
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Regarding the population at risk, the
young age range groups were over-presented
in regard to the age distribution as they
comprise (68%) of the group studied (12
-35 years).
The incidence of sensorineural hearing
loss in this study was 20% in comparison
to the incidence of 14% by Griffiths (1979)
study, and lower than those given by Kerr
et al (1975) of 49% , and Browning (1982)
of56% which were all done on patients
exposed to minor head injury.
Change in hearing may be contra-lateral
or ipsi-lateral to the side of injury
but it was commonly found to be a bilaterally
high tone deficit, mostly around 4 kHz
in comparison with previous study by Schuknecht
et at (1979), who found that a bilaterally
low tone deficit was mostly around 0.5-1
kHz and also reported fluctuations in
hearing which he explained as being the
result of the pressure changes in the
inner ear due to disturbed flow in the
cochlear aqueduct. No fluctuation in hearing
was observed in our study.
Three months later the situation had changed
quite dramatically because all ten cases
recovered completely in this period. This
was attributed to reversible pathology
affecting the auditory system, i.e. they
had suffered a concussion type injury
reported previously by Toglia et al (1970).
Schuknecht (1969) suggested that severe
gradual hearing loss had occasionally
been established several months later
due ~~ to secondary degeneration. In contrast,
our study which showed complete recovery
in all patients.
Griffiths (1979), considered the Volley
theory of hearing to where the whole
cochlea
is thought to be involved in the reception
of low frequency sounds and pathology
such as edema in the labyrinth may
explains the low frequency loss. It seems
likely that the lesion that lies in the
peripheral labyrinth is possibly due to
edema R or hydrops, both of which subsided
with an excellent prognosis, Causes of
high frequency loss are similar to presbyacusis
or severe acoustic traua. Schuknecht
et al (1953), described their t 1,
findings m the audiovestibular system of
cats which were subjected to head blows.
The major changes were seen in the I 2,
middle of the basal turn of the cochlea
around 4 and 8 kHz area, A blow on
the head creates a pressure wave in the
skull which is I 3. transmitted through
bone to the cochlea causing intense acoustic
stimulation i.e. concussion and intense
acoustic stimulation are the probable
causes for hearing 1oss (8)
It appears that the acoustic injury is
permanent, the r pathological changes
of concussion temporary and thus any ~
5. expected recovery is likely to take
place in the first-three months. Makishima
et al (1976) stated "that, (sensorineural
deafness occurs more frequently with a
blow to the occipital region, than in
blows to the other parts of the head.)
Griffiths (1979) stated that, the temporal
region is the commonest to show this effect.
In the present study the incidence of
hearing loss was 50% for! temporal injuries
followed by 30%, 20% and 0% for occipital,
frontal and vertical injuries respectively.
Such findings confirmed the previous
results of Griffiths (1979). In frontal
If injuries the distance that a pressure
wave has to travel through the cranium
to the audiovestibular system is great
with a reasonable damping effect of the
cranial contents; only the more severe
injuries (such as those sustained in car
accidents) produce a more severe hearing
loss, but in temporal injuries there is
less damping and impacts produced a more
serious hearing loss in ~ the ipsilateral
ear and a lesser loss in the contralateral
ear (2).
Toglia et al (1970), suggested that whiplash
injuries cause injuries to the sympathetic
nervous system and to vascular structures
in the neck causing ischaemia of the labyrinths
and their central connections. Makishima
(1975) stated that, disturbances in the
brain stem can be observed after minor
head injury. He measured post traumatically
cochlear potentials of test animals, and
determined the evoked responses in the
brain stem. They found that the cochlear
potential was normal but there is disturbance
in the brain stem evoked responses. This
suggest that central hearing impairment
is frequent in minor head injuries. In
this study eight cases (80%) out of the
ten cases with sensorineural hearing loss
were found due to cochlear lesion as manifested
by the audiological tests and brainstem
evoked response study, while the other
two cases (20%) were found to be due to
retrocochlear lesion, but central hearing
impairment was not found in our series.
The cause of retrocochlear hearing impairment
may be due to formation of haematoma which
resulted in compression of the cochlear
nerve but under treatment and observation,
haematoma subsided gradually and complete
resolution with complete recovery of hearing
loss occurred within three months(8).
Post traumatic amnesia was found in this
study less than five hours and this consistent
with results reported by Griffiths (1979)
and Browning et al (1982).
Conclusion:
In this study it is concluded that, the
incidence of sensorineural hearing loss
following minor head injury is a temporary
phenomenon as all cases recovered within
three months. Cases with sensorineural
hearing loss were more due to trauma to
a moving head than to a fixed head.
-Minor head injuries with amnesia resulted in vertigo in 16 patients, the association of vertigo with of sensorineural loss is common. All cases recovered completely within three months duration, results were explained on the basis of labyrinthine concussion.
-Tinnitus is another sequel of minor head injury with amnesia and found to occur in 26 patients and the association with sensorineural loss was 60% .All conditions completely recovered in three months, and explained on similar basis as above.
References:
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