ENT: Embryology

ENT Embryology Inner ear Early 4th week = thickening (optic placode) forms on sides of head 5-8 weeks = placode à inner ear Continues to mature until term Middle ear 32nd day = 1st pharyngeal pouch à expands to cavity which medially becomes eustacian tube Expands by apoptosis to leave ossicles suspended in cavity Outer ear 1st pharyngeal groove (from 3 pairs of auricular hillocks) fuse to form pinna Cartilage begins to ossify in 6th month Functions Pinna = funnels sound Vibrates TM à malleus, incus and stapes à footplate à inner ear à generates action potentials à CN VIII à brain Examination Otoscopy Tympanometry OAE – new born hearing screen Brain stem evoked response audiometry – looking for brain stem responses – usually done under sedation Distraction testing – noises around child Visual reinforcement audiometry – turning to the sounds of the speakers. Once turned a visual stimulus appears to reinforce the behaviour of turning. Performance testing – on hearing tone asked to press button / put toy in hole. Pure tone audiometry Hearing Tests Otoaccoustic emissions (OAE) (new-born hearing screen) Present in 98% of normal ears Sound generated in inner ear Correlated to normal outer hair cells Absent if loss >30dB Detects physiological response from the outer hair cells in the cochlear (present in 98% of normal babies) Detects an element of sensorineural deafness Auditory brainstem response test (ABR) (if fail hearing screen) Records electrical activity in CN VIII “Click” stimulus to ear at 35dBnNL Tests both cochlear and nerve Therefore good test for high risk e.g. meningitis/congenital infection Assess evoked electrical signals by surface electrodes from within hearing pathway in response to sounds Tests the entire nerve pathway Typanometry Type A = normal. Peak at 0 Type B = no peak. Abnormal middle ear function Type C = Negative middle ear pressure. Eustacian tube dysfunction No line. Vol > 2.5cm2 = Perfed eardrum / functioning grommets 6-9m – distraction testing 4m-10y – speech discrimination / impedance audiometry 3-4y + – threshold audiometry Sensorineural = no improvement with bone conduction Conductive = tuning fork transmits better on bone Audiometry R conduction L conduction à à O X [ ] ß ß R Bone L Bone Hearing loss: 0 to -20 = normal variation -20 to -40 = conductive } Unless large variation between -40 + = sensorineural } bone & conduction Example shows Right severe sensorineural deafness Rinne & Webers tests Rinne = tuning fork struck & held on mastoid until no longer heard Then hold near ear & see if it is heard again If then heard = positive test = NORMAL If not heard = negative test = ABNORMAL NEGATIVE SIDE IS ALWAYS ABNORMAL NB: If testing a sensorineural deaf ear test will be positive – therefore use Weber test as well to help Weber = Place tuning fork in centre of forehead and see which ear sounds louder Weber louder in Rinne –ve ear = Conductive Weber in the opposite ear = Sensorineural Criteria for on-going testing Parental concern Meningitis, chronic effusion, craniofacial abnormality FH of sensorineural hearing loss SBCU babies with errors in OAE/ABRT or > 5d on IPPV Jaundice with exchange transfusion Neurodegenerative/developmental problems Confirmed syndrome assoc with deafness e.g. Downs (50% have mod-severe hearing loss) Vocal Cord dysfunction Intermittent daytime wheezing Cords close inappropriately during inspiration à SOB / cough / throat tighness / laryngeal wheeze / stridor Can co-exist with asthma Paradoxical vocal cord movements Vocal cord paralysis Can be due to surgical correction of TOF/ congenital cardiac / thyroid due to recurrent laryngeal nerve pathway Unilateral à aspiration, coughing, choking with weak breathy cry Vocal nodules Most common cause of hoarseness in children Due to chronic vocal abuse / misuse (extensive rehearsals) Nodules at junction of anterior and middle 1/3 of the phonating edge of the cords. Affect voice production. Acute otitis media Pain, fever, hearing loss Red budging membrane with effusion in middle ear Organisms: strep pneumonia, HiB, moxarella, Grp A Strep, S.aureus Minority are viral 80% recover without antibiotics Rx – amoxicillin à decreased risk of mastoiditis Otitis media with effusion Fluid behind intact TM in ABSENCE of acute infection Peak at 1y & 3-5y Most cases resolve spontaneously in 3/12 Younger onset assoc. with longer duration Can impact on speech development Risk factors Age Season (increase in winter) Siblings with FH Race Attending group childcare Smoke exposure Bottle fed Anatomical problems (e.g. cleft palate) Tonsils/adenoid hypertrophy Rx: Tonsillectomy Grommets Hearing aids if severe Balance Vestibular areflexia – delayed walking. DONT get travel sick Nystagmus, vomiting, falling with LOC Tonsil/Adenoid Hypertrophy Begin to develop 3rd month of gestation Max growth by 1-2y Fully grown by 8-9y à involute Hypertrophy can à prolonged URTIs, mouth breathing, hyponasal speech, recurrent OM, or OSAS Tonsillectomy if: recurrent infection, 2+ episodes of quinsy, OSAS, consider in T21 Adenoidectomy: OSAS, recurrent OM, OM with effusion, Nasal obstruction Complications: primary bleed 0.5-1.5%, secondary bleed 6-10d, damage to soft palate & tubes Obstructive sleep apnoea Noisy breathing, poor sleep quality, daytime sleeping, apnoea’s, Ix with sleep study See respiratory notes for more details Tonsillar exudates Tonsils and adenoids are lymphoid tissues with stratified squamous lining & grooves & crypts (containing cheesy debris = food, mucus, WBCs etc. Lymphatic drainage is jugulo-digastric nodes and upper cervical LNs Sensation from glossopharyngeal and vagus nerves Function: detect and defect against oral & inhaled pathogens à antigen à T-helper à B cells à IgA production Virus – EBV, adenovirus, RSV, Influenza A/B, parainfluenza, herpes, coxsackie B Bacteria Group A haemolytic strep (30%) – inc strep pyogenes Can à direct invasion/toxin production Can à erythrogenic toxin à Scarlet fever Self-limits in 7d (without Abx) Complications: OM, sinusitis, cervical adenitis, quinsy, Scarlett fever, SSSS, Rheumatic fever, post strep glomerulonephritis Other bacteria – other B haemolytic strep, strep pneumonia, HiB, moraxella, S.aureus, anerobes (bacteroides) and other mycobacteruia, neiseria, diphtheria Rx with ABX if: Marked systemic upset Quinsy History of rheumatic fever Increased risk e.g. CHD/Downs Or to decrease infectivity to others Diptheria Corynebacterium Diptheriae Gram +ve bacillus Consider if eastern Europe/Russia/ south-east Asia 1-2d fever + sore throat àpseudomembrane over tonsils, palate and larynx = green/grey and adheres to tissues Affects soft tissues and causes lymphadenopathy High mortality without treatment Sinusitis 4x paranasal sinuses – ethmoid, mastoid, frontal, sphenoid Drain via narrow ostia to nasal cavity Lined by stratified ciliated columnar epithelium Sx: Prolonged URTI with fever + purulent nasal discharge Cough Bad breath Facial pain/headache Painless periorbital swelling (ethmoid) Signs Discharge Inflamed nasal mucosa Pyrexia Occasionally tender palpation/percussion over sinuses Differentials UTRI Allergic rhinitis Periorbital cellulitis Causes / Assoc with Viral URTI Allergic rhinitis Polyps Foreign body Trauma Unilateral choanal atresia Defective cilia (PCD) CF (abnormally thick mucus) Treatment 10-14d oral amoxicillin/erythromycin OR IV cefuroxime/augmentin Topical ephedrine à reduces mucosal oedema à aids drainage Surgery if abscesses form Complications Periorbital oedema/abscess/cellulitis Cavernous sinus thrombosis Meningitis Intracranial abscess Mastoiditis Mastoid has some air in at birth Complete by 10yrs Communicated with posterior aspect of middle ear by narrow aditus ad antrum OM can à mastoiditis Antrum becomes blocked with inflamed mucosa à blocked drainage à empyema Organisms: Strep pneumonia, HiB, Grp A Strep, occasionally moraxella, mycoplasma or pseudomonas Sx: recent OM, fever despite antibiotics, pain in/behind ear, purulent discharge from ear / hearing loss, tender behind ear with swelling and auricular displacement with loss of skin crease Complications: subperiosteal abscess, meningitis, CN VII palsy, cavernous/sigmoid sinus thrombosis, osteomyelitis of petrous temporal bone, intracranial abscess, laryrinthitis Rx: ENT opinion, Abx (3rd gen cephalosporin + vanc/clindamycin Neck lumps Usually in anterior chain, can be posterior chain Common Cervical adenitis – discrete, tender due to URTI / tonsillitis / otitis media / rubella Glandular fever / mumps à salivary gland enlargement Mastoid – mastoiditis à ENT referral Cervical Abscess Rare Thyroglossal cyst – moves with tongue à excision Branchial fistula remnant Thyroid (goitre) = midline TB Lymphoma / Leukaemia Hearing loss Conductive = external / middle ear Sensorineural = cochlear/nerve Mixed = both Deaf = >40dB across speech frequencies (approx 840/yr) Mx of early hearing loss Targeted follow up Early cochlear implant Support with SALT Digital hearing aids Causes of loss Blockage of canal – atresia, wax, FB Perf of TM Otitis media with effusion (glue ear) Disarticulation / necrosis of ossicles Otosclerosis Sensorineural hearing loss Abnormal cochlear/nerve 1.2/1000 children No air-bone gap on hearing tests Mild <40dB Mod 41-70 Sev 71-95 Prof >95dB Causes of isolated hearing loss Neonatal asphyxia/prematurity Toxic – high gentamycin/ bilirubin Genetic – 50% of cases. Mostly recessive, 30% syndromic, Occ Xlinked/mitochondrial Craniofacial Infection (post meningitis) – 10%. Can be late onset. Test at 6-8/52 post infection. 1-4% à bilateral profound loss. Can be progressive. Can get cochlear ossification Trauma Cochlear implant If severe/profound hearing loss AND no benefit from hearing aids Early implant is most benefit at most receptive understanding is gained by 1yr Can be used for loss post meningitis (à fast tract) No minimum age Deafness 4% of all children have mild deafness – mostly glue ear 2/1000 need hearing aid 1/1000 are severely deaf & require special education Conductive = 4% prevalence = middle ear dysfunction Glue ear most commonly Sensorineural deafness = 0.3% prevalence 50% genetic – various types 30% post natal – meningitis, encephalitis, head injury, gentamycin toxicity 12% perinatal – birth asphyxia, severe high SBR 8% intra-uterine e.g. congenital infection (rubella), maternal drugs (streptomycin) Loss of 20dB = little effect Loss of 40dB = impact on speech development Causes Genetic = 50% 80% single gene defect AR 15% single gene defect AD Deafness from chromosomal / syndromes are rare Branchio-oto-renal syndrome. 1/40,000. - Commonest syndrome. Branchial clefts, ear abnormalities & renal anomalies Pendred syndrome, AR – goitre & profound deafness Waardenburg Syndrome, AD – white forelock, different coloured eyes, deafness Usher syndrome – AR, retinitis pigmentosa à blindness & deafness Congenital infection Rubella – now rare. Microcephally, cateracts, deafness, active infection may continue after birth therefore deafness can develop in early childhood CMV – 30% of CMV will have hearing problems, even if asymptomatic 20% will develop hearing loss. Progressive loss Meningitis – E.coli, GBS, & listeria especially. Infection à inflammation of inner ear structures à damage. ? benefit from dexamethasone Bilirubin Part of spectrum of kernicterus May pass the OAE, but will be picked up by ABR Most damage in most unwell infants = reason for lower PT lines in sick prems Drugs – aminoglycosides e.g. gentamycin – risk is overstated is used correctly Sensorineural deafness Lesion in cochlear / auditory nerve / central 1/1000 Risk factors NICU admission Infection (mumps, meningitis) / CMV / Rubella Downs, Noonan’s, Dysmorphism of head & neck FH of hearing aid at <5yrs High SBR (> 340 for term, >240 for LBW) Screening would only find 50% Conductive hearing loss Occurs in downs, cleft palate, turners & facial malformations Hearing Aids Can be used for sensorineural or conductive BUT most conductive have treatable cause e.g. glue ear Therefore mostly in Sensorineural