Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4466_Библиотеки_им_академика_М_И_Перельмана
.pdf
8
https://t.me/medicina_free
N. Türe et al.
of sudden death, sudden infant death syndrome (SIDS), fainting attacks or
abnormal prolongation of the QT interval, a detailed investigation is warranted.
– It is believed that mutant alleles for the KCNQ1 (or, more infrequently, the
KCNE1) gene may be responsible for this syndrome. These genes code for
proteins involved in the transportation of K+ ions. Potassium transport is vital
for both inner ear and cardiac function. The KCNE1 and KCNQ1 gene products assemble to make a transmembranous complex which can remove potassium cations out of the cytoplasm. If potassium ion transport is disrupted, the
myocardium and inner ear may both malfunction, leading to the characteristic
signs and symptoms [10].
• In Cockayne syndrome, patients exhibit dwarsm, atrophied retina and auditory
impairment. The syndrome typically presents between the ages of 1 and 2years.
It is inherited in an autosomal recessive fashion. The clinical picture involves
short stature, a kyphotic spine with fused joints, mandibular protrusion, deep-set
eyes, learning disability, atrophy of the retina, thickening of the skull, dental caries and auditory impairment. Usually, the hearing loss is progressive, sensorineural and bilateral. There is also neurodegeneration in the spiral ganglion and
cochlear and olivary nuclei. The Genetics Home Reference states that the aetiology is mutated alleles of the ERCC6 and CRCC8 genes. The product of these
genes features in DNA repair. When repair does not occur, there is a build up of
defective DNA which prevents the cell from surviving. This then explains why
growth is restricted and ageing occurs prematurely [11].
• Patients with Alström syndrome have retinitis pigmentosa, diabetes mellitus and
cardiomyopathy, and are abnormally short and obese and suffer from progressive
auditory impairment. In some, but not all cases, hepatic and renal failure occurs,
as well as lung disease. The auditory impairment is usually of sensorineural type
and characteristically begins within the rst decade of life. The syndrome is
inherited in an autosomal recessive fashion. The mutated ALMS1 gene has been
implicated in the disorder, although what role the gene product plays is not yet
established [12]. Nadol et al. undertook a histopathological investigation into
cases of Alström syndrome. They found that sensorineural auditory impairment
was associated with degenerative features in the inner and outer hair cells of the
organ of Corti, neurodegeneration within the cochlear ganglion, together with
atrophic appearances of the stria vascularis and spiral ligament. These features
were noted in two cases where the diagnosis had been conrmed by genetic testing [13].
• Cases of Refsum disease exhibit an autosomal recessive pattern of inheritance
and present with retinitis pigmentosa, ichthyosis, polyneuropathy, cerebellar
ataxia and auditory impairment. Patients with Refsum disorder generally live
until the age of 10–20years. In patients older than 20, visual impairment is characteristic. Over half of the cases feature a progressive auditory impairment of the
sensorineural type. Histopathological examination shows the organ of Corti and
the stria vascularis to be degenerated.
1 Pediatric Hearing Loss
https://t.me/medicina_free
There are also a number of causes of auditory impairment where the pattern of
inheritance is X-linked, variable or obscure [4].
1.2.2.3 X-Linked Disorders andOther Disorders
ofVariable Inheritance
• The most frequently occurring genetic cause of nephritis is Alport Syndrome. It
affects 1in 200,000 people. The features of this condition are haematuria, posterior cataract formation, a dystrophic cornea and a dislocated lens. Interestingly,
Alport syndrome occurs at a higher frequency in girls than boys, but the symptoms are more severe in males, with terminal kidney failure often noted between
the ages of 10 and 30years. Without treatment, male cases are fatal before the
age of 30 years. The onset of clinical features is usually before the age of
10years [4].
– Auditory impairment generally affects both ears to the same extent. It can also
be of the sensorineural type, with the greatest loss affecting higher-pitched
sounds. The condition can be inherited in various ways: autosomal dominant
and recessive forms are encountered, but the majority of cases (85%) feature
X-linkage. Mutated alleles for the COL4A3, COL4A4 and COL4A5 genes
have been implicated in the aetiology.
– COL4A3, COL4A4 and COL4A5 encode for collagen of type IV.This mate-
rial is vital to the formation and physiological function of the basement membrane of both the renal glomerulus and the stria vascularis. Within the kidney,
the defective collagen eventually causes the glomerular basement membrane
to fail and thus terminal kidney failure ensues. Exactly how auditory loss
occurs has not yet been established, although Merchant etal. have ascertained
that, within the organ of Corti, there are dysmorphic cells and the basilar and
basement membrane separate [14].
• Norrie disease is a rare disease, resulting in potential blindness, delayed motor
skill acquisition, learning disability and auditory impairment. Its aetiology is a
mutated allele for the NDP gene found on the X-chromosome. This gene encodes
norrin, a signalling molecule involved in development, which causes cells to
divide, adhere to each other or migrate [15].
• It is common for conditions causing congenital metabolic abnormalities to feature sensorineural auditory impairment amongst their presenting features.
Examples include the mucopolysaccharidoses, such as Hurler and Hunter syndromes, and sphingolipidoses, such as Fabry disease [4].
– The features of Hurler syndrome are intellectual disability, excessively short
stature, a kyphotic spine, enlargement of the liver and spleen and auditory
impairment. It shows a pattern of autosomal recessive inheritance. This disorder results from an excess accumulation of heparin and dermatan sulphate
(both of which are glycosaminoglycans). Auditory impairment is usually of
mixed type, but with a marked loss of the higher pitched sounds.
Histopathological examination of the temporal bone indicates positive staining with periodic acid-Schiff of the mesenchymic material and the organ of
Corti has degenerated appearances. It is unusual for patients to live beyond
9
10
https://t.me/medicina_free
N. Türe et al.
the age of 13 or 14. Hunter syndrome shares many clinical features with
Hurler syndrome, but exhibits X-linkage.
– Hunter syndrome is a less severe disorder, and affected patients may live into
their early twenties. Auditory impairment can follow several patterns: conductive, sensorineural or a mixture of the two.
– Another disorder exhibiting X-linkage is Fabry disease. The aetiology
involves accumulated sphingolipids within the endothelium, smooth muscle
and ganglia. Auditory loss usually affects both ears and is mainly sensorineural, with the highest-pitched sounds the most affected. Histopathological
examination of the temporal bone reveals an atrophic cochlear ligament with
sphingolipids deposited within the endothelium of the vessels and the ganglionic cells.
• Trisomy 13 affects 1in 6000 births. The severity of the associated anomalies
present at birth is so high that the majority of such cases are fatal within the rst
year. Babies with the condition are microcephalic, have labiopalatal deformities,
possess extra digits, rocker-bottom feet, ears which are set low and malformed,
have the heart shifted to the right, the scalp is defective and there is intellectual
disability. Histopathological examination of the temporal bone indicates cyst formation in the stria vascularis, an abnormally short cochlea, degeneration of the
saccule and abnormality of the semi-circular canals [4].
• The incidence of trisomy 18 has been estimated at between 1in 5000 and 1in
10,000 live births. The majority of affected infants die within the rst 3months.
However, as many as 13% of such infants may survive up to one year and beyond.
The presenting features are malformation of the external ear, small jaw, prominence of the occiput, abnormality of the intestines and intellectual disability.
Histopathological examination of the temporal bone shows that the stria vascularis has failed to grow to full size, the semicircular canals are abnormal and
there is paucicellularity of the cochlear ganglia.
• The most frequently occurring chromosomal disorder globally is Down syndrome (Trisomy 21). Trisomy 21 occurs in 1 in 1000 of all births, but the frequency greatly increases as the age of the mother increases, with an incidence of
1in 25 births for women over the age of 45. Some of the characteristic features
are a shortened and broad trunk, epicanthal folds, low muscle tone, congenital
cardiac disorders and intellectual disability. Almost 78% of patients with trisomy
21 have auditory impairment, which can be conductive, sensorineural or a mixture of the two. On histopathological examination of the temporal bone, there
may be remnants of the mesenchymal tissue in the middle ear, serous accumulation within the labyrinth and the seventh cranial nerve forms a wider than usual
angle at the genu [4].
• The rst description of Klippel-Feil syndrome was in 1912. The features include
at least two vertebrae in the neck being fused from birth, high scapula, spina
bida, an asymmetric appearance to the face, muscular spasticity and congenital
cardiac disease. If Klippei-Feil syndrome occurs together with a sixth cranial
nerve palsy in both eyes and deafness, the term Wildervanck syndrome is used.
Auditory impairment is profound and sensorineural in kind, although some
1 Pediatric Hearing Loss
https://t.me/medicina_free
reports also mention conductive pattern decits or a mixed type of impairment
being present. The inner ear is hypoplastic, and the osseous and membranous
labyrinths both fail to develop. The condition exhibits genetic heterogeneity.
• In Wildervanck syndrome, also termed cervico-oculo-acoustic dysplasia, the
vertebrae of the neck are fused, the neck is shortened and the hairline is low at
the back (i.e. features of Klippel-Feil), plus the eyes are deepset, there is auditory
impairment of both sensorineural and conductive type and the patient has difculty looking to the side. More girls than boys are affected. The disorder is inherited in a dominant fashion and is X-linked [4].
• Albinism occurs when the production or distribution of melanin is abnormal. In
patients with oculocutaneous albinism, the skin, hair and eyes are all unpigmented. This disorder has an autosomal recessive pattern of inheritance. The
majority of patients with albinism who present with sensorineural deafness have
oculocutaneous albinism. The auditory impairment ranges in how severe it is [4].
• It is believed that otopalatodigital syndrome exhibits X-linkage and has a recessive pattern of inheritance. Some of the characteristic features are cleft palate,
sh mouth, clinodactyly, prominence of the forehead, wide-set eyes and antimongoloid slanting of the palpebral ssures. The ossicles are also malformed,
which results in auditory impairment of the conductive type [4].
• There are a number of other syndromes inherited in an X-linked fashion which
cause auditory impairment, such as oculocraniosomatic syndrome, myoclonic
epilepsy with ragged red bres, MELAS (mitochondrial encephalopathy, lactic
acidosis and stroke-like episodes) and MIDD (maternally inherited diabetes and
deafness) [4].
11
1.2.3 Signs andSymptoms
The clinical history should include the following aspects [4]:
• History of the pregnancy
• Events during birth
• Development after birth
• Family history
The following are areas of the physical examination or investigation that may
reveal a syndrome underlying auditory impairment [4]:
• Otoscopy
• Ophthalmoscopy
• Dermatologic examination
• Cardiovascular examination
• Renal examination
• Oral cavity and oropharyngeal examination
• Endocrine or metabolic studies
12
https://t.me/medicina_free
• Chromosome examination
• Nervous system examination
• Skeletal system examination
• Craniofacial examination
The following are features of the presentation which suggest an underlying syn-
drome responsible for auditory impairment [4]:
• When examining the ears, the following ndings are signicant
– An abnormal pinna is seen in the Treacher-Collins and Goldenhar syndromes.
– An atretic or stenosed external auditory meatus is also seen in these two
syndromes.
– Preauricular pitting may be part of a branchiootorenal syndrome.
– Preauricular skin tags are seen in Goldenhar syndrome.
– Radiological evidence of an enlargement of the vestibular aqueduct may be
seen in Pendred, Kabuki, Turner or Opitz-Frias syndromes.
– Lopped ears may be part of Down syndrome or otopalatodigital syndrome.
– Cup ears are part of Pierre-Robin syndrome.
– Undersized ears are seen in Treacher-Collins, Goldenhar, rst branchial cleft,
Möbius and Duane syndromes
• When examining the eyes, the following ndings are signicant [4]:
– Cataracts may indicate congenital rubella.
– Coloboma may be part of the CHARGE syndrome: coloboma, heart abnor-
mality, atretic choanae, growth retardation, genital and ear anomalies.
– The canthi are displaced in Waardenburg syndrome.
– There is also heterochromia of the iris in this condition.
– Keratitis is observed in Cogan syndrome.
– The eye muscles are weakened in Duane syndrome.
– Atrophy of the retina is seen in Cockayne syndrome.
– Usher syndrome patients have retinitis pigmentosa.
– The retina shows a degenerative change in cases of Alström syndrome.
– Children who have been blind since birth and present with a retinal pseudotu-
mour may have Norrie syndrome.
N. Türe et al.
1.2.4 Diagnosis
There is no consensus for a routine laboratory screening of paediatric patients with
hearing loss. Some of the laboratory tests which may be of value in particular cases
include [4]:
• Genetic screening, including a genetic panel of hearing loss disorders
• Full blood count including differential
• Urea and electrolytes
• Blood glucose
1 Pediatric Hearing Loss
https://t.me/medicina_free
13
• Urea, nitrogen and creatinine blood level
• Thyroid function tests
• Urine analysis
• Fluorescent treponemal antibody absorption (FTA-ABS)
• IgM titres for specic antigens
• Autoimmune screening blood
The following are the imaging modalities of the most value in diagnosis [4]:
• Computed tomography (CT)
• Magnetic resonance imaging (MRI)
• Ultrasound examination of the kidney
• CT Imaging
– CT imaging can be set up to produce slice images at a distance of no more
than 1mm apart. The resulting scan is of high resolution and allows the osseous anatomy, the inner ear and the ossicles to be clearly seen.
– CT is valuable in nding cases where surgery may be able to improve senso-
rineural hearing impairment. It also helps to evaluate the degree of dysplasia,
with less dysplasia offering an improved chance of beneting from treatment.
Since CT imaging reveals an abnormality in as many as 30% of cases of auditory impairment, this imaging modality plays a key role in diagnostic assessment. As an example, patients with Pendred syndrome often show enlargement
of the vestibular aqueduct and Mondini dysplasia on CT [4].
• The ability to visualise soft tissues means that MRI is especially useful when
assessing the inner ear, the internal auditory canal and the cerebellopontine angle.
• Ultrasound examination of the kidney is helpful diagnostically if a renal anomaly
is being considered [4].
Auditory assessment:
• This involves the use of methods designed to evaluate auditory loss, such as
audiometry and tympanometry [4].
• There are tools which may be used to diagnose and qualify auditory loss in neo-
nates even within the rst 24h after birth. These methods have a high level of
reliability and validity, for example [4]:
– Auditory evoked potential/auditory brainstem response (AEP, ABR)
– Audiometry
– Tympanometry
– Acoustic reex threshold measurement
– Otoacoustic emissions (OAE)
14
https://t.me/medicina_free
N. Türe et al.
1.2.5 Treatment
• Pharmacotherapy: Drug treatment is appropriate for diseases of the middle ear,
such as otitis media [4].
• Amplifying hearing
– The aim of amplifying hearing is to make use of whatever auditory function
is available, so that, as a minimum, patients become accustomed to their surroundings and begin to develop at least rudimentary speech. In most cases,
implantation of an amplicatory device up to the age of 6weeks is successful.
– There are several types of devices which may be used, including conventional
analogue devices, digital hearing aids, aids which boost osseous conduction
and bone-anchored hearing aids. There are a number of devices being developed which are for implantation in the middle or inner ear [4].
• Assistive listening equipment and personalised devices [4]:
– Devices for individual use, e.g. FM (frequency modulation) trainers, are
designed to reduce how noisy the signal is in environments where this presents signicant difculties, such as a classroom.
– There are several devices to assist with telephones, such as ampliers, cou-
pling devices to match specic hearing aids and specially adapted telephones
for deaf individuals who nd an ordinary telephone too hard to use.
– Televisual devices may offer closed captioning, which helps patients with
severe auditory loss.
– Signalling devices provide a visual warning instead of an auditory signal. For
example, these devices can warn the user that the doorbell has rung, the telephone is ringing, an alarm is sounding or a child is crying.
• Surgery
• Operative interventions may be needed for some anomalies of the external or
middle ear, affecting one or both ears [4].
1.2.5.1 Cochlear Implants
A cochlear device is an electronic device which can transduce a sound signal into
electrical impulses to be transmitted to the cochlear nerve. Such devices are especially benecial where an individual is not assisted in hearing by straightforward
amplicatory techniques [16–18].
Prior to the procedure, an MRI scan may be helpful to conrm the integrity of the
cochlear nerve. CT imaging is a routine way of assessing pathology affecting the
cochlea.
There are signicantly improved linguistic abilities in patients under the age of
5years following a cochlear device being implanted. The operation may be undertaken when the child is one year; consideration is given to earlier surgery in cases of
hearing loss resulting from meningitis.
Alzhrani etal. compared the outcomes from cochlear implantation in paediatric
patients with auditory impairment either secondary to a syndromic condition, such
as Waardenburg, Usher or Dandy-Walker syndromes or albinism or of nonsyndromic cause. The outcomes in both groups were similar, with the perception of
1 Pediatric Hearing Loss
https://t.me/medicina_free
sound, the ability to identify spoken words and the pure-tone perception not differing greatly [19].
15
1.3 Conductive Hearing Loss
Whilst it has been well established that sensorineural hearing loss is present from
birth in between 1in 3 children with any kind of sensorineural loss, the incidence of
conductive hearing loss at birth is less clear, but likely much lower. CHL occurs
secondary to obstruction, abnormal function or anomalous development of the
external auditory canal/meatus, tympanic membrane or the middle ear apparatus. A
trial involving 234 children under the age of one year who were referred for diagnostic evaluation following neonatal auditory screening found a rate for congenital
CHL of 2.97 per 1000 infants, whilst 4.36 per 1000 of this group had middle ear
disease (not always resulting in auditory impairment). The researchers comment
that, “In the literature pertaining to CHL in children, the emphasis is on cause rather
than severity, making prevalence data difcult to compare” [20]. Despite considerable research efforts devoted to evaluating the persistence of problems in acquired
or congenital paediatric CHL, particularly in relation to otitis media with an effusion, no denite consensus on the ndings has yet been reached [21–24].
1.3.1 CHL Present at Birth
CHL present from birth is rarely the result of anomalous middle ear development.
The various conditions responsible for anomalous middle ear development are
CAA, in cases in which the external ear canal is not present or is stenosed, coupled
with underdeveloped ossicles within the middle ear and some minor anomalies of
the auditory system [25]. In the latter cases, there is no abnormality of the auricle,
the external auditory meatus is open and complete and the ear drum is whole, but
the ossicles are deformed, immobilised or otherwise disrupted. Such minor anomalies include congenital ankylosis of the stapes, the persistence of the embryonic
stapedial artery, xation of the malleus by the formation of a bony bar and the
absence of the oval window. The resulting auditory impairment may range in severity from slight effects to severe deafness and may not be apparent on neonatal auditory screening. Thus, diagnosis may not occur until a child is old enough to cooperate
with auditory behavioural tests. Some of the minor anomalies may also occur in
cases of CAA, in particular malleus xation and incudo-malleolar xation [1].
1.3.1.1 Congenital Aural Atresia
CAA occurs at a frequency of between 1in 10,000 and 2in 10,000. CHL associated
with this condition is typically moderate or severe. The threshold for bone conduction is typically normal. In approximately 70% of cases, atresia and microtia affect
only one side. The condition is more frequent in males than females and the affected
side is usually the right. It is not yet known why CAA demonstrates these
16
https://t.me/medicina_free
characteristics. There are also ethnic factors at play, since atresia and microtia are
more common in individuals of Hispanic or Asian ancestry, particularly if they originate from Ecuador. Whilst the aetiology is still obscure, one theory is that when the
auditory meatus and middle ear fail to grow, the rst pharyngeal arch cannot complete its transformation. There is evidence linking CAA to abnormality of chromosome 18, particularly where microtia does not occur, which is the case in a minority
of patients with CAA [26]. There is also a competing hypothesis that foetal positioning in utero plays a role by restricting the vascular supply [1].
In cases where microtia is involved (the majority), recognising CAA is unproblematic. Nevertheless, in a minority of cases, there is a normal-sized ear, so this
diagnostic clue is absent. Therefore, otoscopy is essential to identify the state of the
auditory meatus. The diagnostic evaluation also needs to involve assessing potential
abnormalities of the kidney, spine, and skull and face bones. CAA occurs in association with some syndromes, notably hemifacial microsomia in Goldenhar syndrome
and Treacher Collins syndrome [1].
N. Türe et al.
1.3.2 Acquired CHL
1.3.2.1 Otitis Media withEffusion
Many young patients have uid present in the middle ear, but do not show any signs
or suffer from any symptoms that imply an infection, whether acute or chronic. It
has been calculated that, on average, there are always around 20% of children who
have a middle ear effusion. Indeed, it has been suggested that nearly all children
have at least one middle ear effusion over the course of childhood [27]. OME is
frequently seen after an infection of the upper respiratory tract or may be a complication of acute otitis media. It generally resolves spontaneously. There is an elevated
risk of OME compared to the general paediatric population in particular groups. For
example, OME is more common when the patient has Down syndrome, as a result
of relative muscular hypotonia. It is also much more common in cases of cleft palate, with a frequency approaching 100%. This is attributable to the anomalous position where the levator and tensor veli palatini muscles insert on the eustachian tube,
leading to difculty in actively opening the tube [28–30]. Boys are also at heightened risk, as are children who are immunodecient, have dyskinetic cilia, are formula fed or where there is a smoker in the house. Other risks include having more
brothers or sisters in a household and attending a childcare facility; the latter is the
strongest risk factor [31]. Tympanometry reveals a type B (at) pattern in around
85–100% of cases with OME [32]. While some treat this as a diagnostic nding, it
is important to note that this abnormality is also seen even with no effusion present,
such as in cases of tympanosclerosis or following tympanic membrane repair. Thus,
it has been argued that the best way to diagnose OME is to make use of pneumatic
otoscopy [1].
1 Pediatric Hearing Loss
https://t.me/medicina_free
17
1.3.2.2 Conductive Auditory Impairment Linked toChronic
Otitis Media
The denition of chronic otitis media (COM) generally includes perforation of the
eardrum, whether cholesteatoma is present or not. Most cases of tympanic membrane perforation occur in the setting of prior tympanostomy tube placement or
simply as a consequence of myringotomy. Generally speaking, the tubes are placed
in the anteroinferior quadrant and do not result in conductive auditory impairment.
Where CHL is a result of a perforated eardrum, the loss typically affects lower frequencies. There is a correlation between the increasing size of the perforation and
more severe hearing loss; however, where the perforation occurs does not seem to
inuence how severe the auditory impairment becomes [33]. Prior to myringoplasty,
the extent of auditory loss should be quantied using audiometry to calculate the air
and bone conduction thresholds. The outcome of tympanic repair in children is
inuenced by factors related to both the patient (i.e. intrinsic) and the clinician (i.e.
extrinsic). Patient-related factors include how old the child is, whether there is
drainage of liquid from the ear, if the eustachian tube continues to malfunction,
whether the condition is uni- or bilateral, the general state of health and where and
how large the perforation is. Factors related to the surgeon include the approach
used, the method followed and how experienced the surgeon is [34, 35]. It is likely
that the risk factor of greatest signicance is patient age, with patients aged under
4years generally faring less well than those above that age [36]. However, it has not
yet been established at what age the outcome has the highest probability of success.
Whether the condition is uni- or bilateral also plays a key part [35]. There are a large
number of ways to conduct tympanic repair in children, including myringoplasty
using fat with or without hyaluronic acid for grafting [37, 38], underlay and overlay
or lateral graft applications. For tympanic repair to have the maximum chance of a
successful outcome, the patient and surgeon factors need to be optimised and clinicians should learn from evaluating their own outcomes in practice and adjusting
their practice so as to favour those techniques most associated with success [1].
1.3.2.3 Tympanosclerosis
Tympanosclerosis occurs where persistent or repeated inammatory episodes
affecting the middle ear lead to brotic scarring, which may result in ossicular
immobilisation and therefore an auditory impairment of the conductive type. Where
tympanosclerosis affects only the eardrum (i.e. myringosclerosis), it typically does
not result in any measurable hearing loss, but where there is ossicular involvement,
it may lead to a slowly progressive loss conductive in nature. Patients who have suffered repeated infectious episodes of the middle ear, as well as those with tympanic
thickening, may have this type of progressive auditory impairment, and in such
cases, the possibility of the ossicles having become xated through brosis should
be considered.
1.3.2.4 Cholesteatoma
Cholesteatoma is a condition wherein the stratied squamous epithelium proliferates beyond the normal level—on the external surface of the tympanic
Соседние файлы в папке Библиотека им академика М.И. Перельмана