U14W1: Ear disease Flashcards
What is the function of CN7 - facial nerve?
GSA - skin behind the ear
SVA - taste to anterior 2/3 of tongue
GVE - parasympathetic to the lacrimal, sublingual and submandibular gland.
SVE - muscle of facial expression
How can we differentiate between different intensities, durations and locations of sound?
Different patterns of action potential are generated in the sensory neurons in the spiral and vestibular ganglia.
What is the function of CN8?
Special somatic afferent fibres for hearing and balance
What is the circuitry/nuclei for the motor function of the facial nerve?
Corticobulbar tract
Projections from the facial motor area of the precentral gyrus to the Facial motor nucleus in the lower pons (near junction with medulla) to synapse with a LMN. **
Upper - bilateral
Lower - contralateral
LMN - not forehead sparing.
What is the ciruitry/nuclei for the parasympathetic function of the facial nerve?
Originates in the superior salivatory nucleus and the lacrimal nuclei in the lower pons.
Synapse in the pterygopalatine - projections to the lacrimal gland
Synapse in the submandibular ganglion - projections to the submandibular and sublingual gland.
What is the circuitry for the sensory element of the facial nerve? **
Responsible for taste from anterior 2/3 of tongue. Solitary nucleus in the brain stem, vpm nucleus of thalamus, to gustatory cortex in the insular, abd gustatory association areas in the frontal lobe.
Also porojection to amygdala and hypothalamus.
What are the potential complications of acute otitis media?
- Prolonged obstruction of e,tube and fluid accumulation in middle ear - pressure is transferred to tympanic membrane causes perforation of TM leading to discharge from ear and pain relief. In some causes pain transfers to the inner ear causing vestibular or labyrinth problems - poor balance
- direct spread to mastoid air cells - mastoiditis or abcess.
- Severe infection - sepsis, fevers and seuixures, intracranial invasion - meningitis, brain abscess.
What are some risk factors for acute otitis media?
Tobaccos smoke - inc nasopharyngeal streptococcus pneumonia
Down syndrome - alters anatomy of e.tube
Age 6-16 months - immaute anatomy and immunity
Lack of immunizations - no memory against pathogens
Lack of breast feedings - colonisation of nasopharynx with bacteria pathogens
Day care children - overcrowding and high risk of infection spread.
What is the key pathophysiology underpinning acute otitis media?
Oftens starts as URTI such as SP or RSV
Causes inflammation and edema of respiratory muscoa and up the e. tube
Obstruction of e.tube causes secretions to accumulate in the middle ear.
Negative pressure in the middle ear, pulls viruses and bacteria into it causes infection and inflammation in the middle ear
Increased pressure - otalgia and bulging TM
Cytokines - fever, fussy and poor feeding
Neutrophilic infiltrate of middle ear - cause yellow or white pus to accumulate behind TM - can discharge through perforated TM or the mastoid.
What are the main treatments of acute otitis media?
Consider ENT or paediatric referall
Consider a delayed first-line antibiotic ear drops and oral - amoxicillin
Regular doses of paracetamol or ibuprofen for pain.
Advise on hygiene - avoid swimmine and fluid in ear.
Surgery if complications - tympanoplasty
What is an audiogram?
Graph produce in pure tone audiometry - measures the dB and Hz of detectable sound, plot and compare to normal hearing range
Patient wears headphones in enclosed sound proof room, sound is directed to one ear at a time.
Can identify discrepancies between ears, bone conduction and air conduction,
What is the normal hearing range in adults?
20dB or lower
250-8,000 Hz.
What are the different stages of hearing loss?
Quietest sound heard is between
Below 20dB - norm
up to 40dB - mild
Up to 70dB - moderate
Up to 95dB - severe
Over 95dB - profound.
What is the purpose of a CT in the diagnosis of auditory problems?
Used when conductive hearing loss is suspected
Used to look for structural abnormalities in the ear and surrounding structures
Identify bone or tumour abnormalities
Check for complications such as intracranial abscess or tegmen erosion.
What clinical tests can be used to rule out neurological consequences from ear disease?
CT - to detect a thin tegmen.
Drain extradural abcsess - look for CSF leakage - clear fluid out of ear or MRI with gadolinium.
Risk of meningitis or intracranial abscess.
What is the use of amoxicillin in acute otitis media?
Clinical: delayed antibiotic prescription, recommended ear drop +/- oral, 1st line antibiotic choice. Against H.influenza, and S.pneumonia
Chem: Beta lactam ring - mimics D-Ala-D-Ala
Pharm: competitive antagonist at Transpeptidase (PBP), covalent inhibitor with serine residue
Physio: inhibit cross linking of peptidoglycan, inhibit cell wall synthesis, causes cell lysis.