Ossicle/Otology

Otology and Neurotology

NEUROLOGY REVIEW

Multiple Sclerosis - multiple demyelinated areas in CNS, “remissions” and “exacerbations”, paresthesias AND weakness (most neuro dz is one or the other), EOM’s affected, vertigo, CN7 involvement, internuclear ophthalmoplegia is pathognomonic

• Charcot Triad - nystagmus, slurred speech, intention tremor
• Diagnosis - MRI findings, incr IgG in CSF with oligoclonal banding

Myasthenia Gravis - M>F, eye weakness in 90%, facial weakness in 70%, pharyngeal weakness, nasal regurg, abnl fatiguability of skeletal mm, reflexes preserves, no nystagmus, no vertigo.

• Tensillon test for diagnosis (short-acting cholinergic).

Amyotrophic Lateral Sclerosis - hyperreflexia, weakness, mm atrophy, fasiculations and fibrillations (esp tongue), dysarthria, upper and lower motor neuron signs, ocular nuclei spared

Pseudobulbar Palsy - affects motor tracts of brainstem nuclei (Bilat corticobulbar tracts), trouble w/ speech, facial extpression, tongue motion, chewing, swallowing, breathing.

Guillain-Barre - Proximal and distal weakness with paresthesias, areflexia and hypotonia, facial diplegia in 50%, respiratory weakness, ocular weakness

• Increased CSF protein and cells

Wallenburg’s Syndrome - PICA thrombosis> Lateral Medullary syndrome. Vertigo, nystagmus, Horner’s, dysphagia, hypotonia, ataxia, decr pain and temp sensation of IPSI face and CONTRA body

Vertebrobasilar Syndrome - vertigo, hemiparesis, dysarthria, vomiting, drop attacks

Migraine - Abort with ergotamine

FACIAL NERVE

Hemifacial Spasm - Irregular contraction of of side of face. Orbicularis oculi and perioral muscles affected

• Primary - electrophysiologic testing is diagnostic and showing synchronous firing rate ~350/sec.
• Secondary - from tumor or cholesteatoma. Asynchronous firing rate.

Blepharospasm - Always bilateral, asynchronous firing with normal rate ~50-70/second

Melkerson's - Recurrent facial paralysis, facial edema, fissured tongue (or furrowed tongue)

Mobius Syndrome - Bilateral congenital facial paralysis with unilateral or bilateral VI palsy

Repairing the Facial Nerve:

• Primary Anastomosis - Best overall option if possible. Do epineural repair except at Pes Anserina, then do fasicular repair.
• Cable graft (from sural n.) - for gaps > 1.5cm usually.
• XII --> VII Jump - Only when proximal VII not available. Within 18 months of injury.
• NERVE REGROWS 1MM PER DAY !
• Muscle transfer - when you can't use nerve.

EMG - tests voluntary units

• Fibrillation potentials = denervation (takes 14-21 days to see).
• Polyphasic action potentials = reinnervation.

Trauma - wait 72 hours after injury for ENOG

• Neuropraxia - conduction block without structural damage.
• Axonotmesis - Degeneration of myelin sheath without dysruption of neurolemnal sheath.
• Neurotmesis - Dysruption of nerve trunk.
• Frontal branch least likely to return after injury.
• Greater auricular nerve most likely nerve injured in rhytidectomy.
• Frontal branch most common 7th nerve branch injured in rhytidectomy (lies just superficial to periosteum over zygoma).

INFECTION AND ITS COMPLICATIONS

Acute Necrotizing OM - β-hemolytic Strep, "sick kids", necrosis of soft tissues and bones of middle ear
Acute Mastoiditis - S. pneumo, Strep pyogenes, Staph
Otitis Externa - Staph, Fungi including Candida and Aspergillus niger
Tuberculous Ear Dz - multiple perforations, oroless discharge, pale granulations, hearing loss out of proportion
11% complication rate after PET placement - otorrhea most common.

Osteoma - singular, large, pedunculated, unilateral, at bony-cartilaginous junction.
Exostosis - Most common EAC tumor, bilateral, multiple. Related to cold water (surfers).

Winkler's - Painful nodule @ helix, AV anastomosis, chondrodermatitis nodularis helicus

Complications of AOM (Suppurative):

• Subperiosteal abscess - most commonly post-auricular. Also Zygomatic or Bezold's (extending into SCM)
• Facial Paralysis - through dehiscence in bony canal (30%) or erosion by cholestatoma
  
• Labyrinthitis - 2' fistula in Lateral SCC. Can be serous or suppurative
• Petrositis - Petrous Apex pneumatized in 30% of healthy tbones.
  • Gradiengo's Triad - OM, CN VI paresis, CN V with pain or paresthesia
• Coalescent Mastoiditis - Loss of bony septations in mastoid
• Meningitis - Most common intracranial complication. CSF with high protein, low glucose.
• Epidural Abscess - Persistent headache, some releif with drainage from ear. 2nd most common complication of AOM after mastoiditis.
• Subdural Abscess - Rare. Headache, malaise, focal seizures, hemiplegia, from thrombophlebitis or direct extension.
• Brain Abscess - Most frequent cause of death from AOM. Most frequent site is temporal lobe followed by cerebellum. Elevated ICP, Thrombophlebitis.
• Lateral Sinus Thrombosis - spiking picket-fence fevers, papilledema, Queckenstedt's Test (no increase in CSF pressure when ipsilateral jugular vein compressed). Greisinger's sign (tenderness over mastoid area from extension through mastoid emissary vein).
• Otic Hydrocephalus - Elevated ICP without brain abscess following OM. Clear CSF. Sxs include headache and CN VI palsy. Rx is repeated LP's.
• Pneumococcus - Bug with highest risk for intracranial complications.

AUDIOLOGY QUICKIES

Speed of sound = 300m/s or 1100f/s
Velocity = Wavelength x Frequency
N dB = 20 x log (P1/P2)
Standard Pressure = .0002 dynes/cm2
Resonant Frequency of EAC = 3kHz
TM Surface Area = 70-80mm2, pars tensa = 55mm2
Footplate Surface Area = 3.5mm2
Lever Ratio of ossicles = 1.3:1 or 2.5dB
Hydraulic Action Mechanical Advantage of TM:Footplate = 17:1 or 25dB
Combined mechanical advantage of lever and hydraulic advantages = 22:1 (1.3 x 17)

Speech Recognition Testing (SRT) uses Spondees
Discrimination Testing used phonetically balanced phrases
Stenger's - when Pure Tone Average does not agree with SRT and descrimination. Performed to detect malingering of unilateral loss. If sound is presented to both ears, patient will deny hearing in the ear with the feigned loss. If sound is presented to the good ear at a suprathreshold level, simultaneous to a louder sound in the questionable ear, a malingerer will localize the sound to his "bad" ear, and therefore deny hearing anything at all.

Masking necessary when AC threshold is 40dB greater than in contralateral ear.

OSHA Sound Exposure Guidelines

• 90dB x 8hr
• 95dB x 4hr
• 100dB x 2hr

DEAFNESS & SYNDROMES

Rubella - cataracts, cardiovascular abnormalities, retinitis

Cogan's aka nonsyphillitic interstitial keratitis. Vertigo with tinnitus, progressive SNHL. Autoimmune etiology. Rx is Steroids

Syphilis - bilateral asymmetric SNHL with vestibular symptoms (like Meniere's)

• Hennebert's Sign - increased mobility of footplate, positive fistula test but no fistula
• Tullio's Phenomenon - vertigo with loud noise
• Histo of Syphilis - Osteitis with mononuclear leukocytosis, obliterative endarteritis, endolymphatic hydrops
• Congentical syphilis associated with saber shins, Hutchinson's Teeth, short stature, interstitial keratitis (corneal opacifications), frontal bossing

EAC Stenosis - normal pinna usually means good middle ear structures. Correct at 4-5y if bilateral >15y if unilateral.

• CN VII takes abrupt turn anterior at 2nd genu (caution)

Congenital Hearing Loss 90% are autosomal recessive

• Michel - complete aplasia
• Mondini - cochea is single curved tube. Cochlear aqueduct is patent. High risks of otic hydrocephalus and meningitis. Also risk of CSF leak from spontanous window fistula. Autosomal Dominant.
• Scheibe = cochlear-saccular aplasia (pars inferior) with normal bony labyrinth and pars superior. Profound SNHL, only hears very low frequencies.
• Alexander - cochlear duct aplasia, hi frequency SNHL.
• Bing-Siebenmenn - membranous vestibular abnormality.

Congenital Deafness Syndromes

• Tietz's - AD, albinism, SNHL, absent eyebrows
• Waardenburg's - AD, wide medial canthi, confluent eyebrow, white forelock, abnormal tyrosine metabolism, SNHL in 20%.
• Apert's - AD, premature closure of cranial sutures, syndactyly, CHL secondary to stapes fixation.
• Klippel-Feil - AD or AR, F>M, SNHL with middle ear abnormalities, fused cervical vertebrae, spina bifida, EAC atresia.
• Marfan's - AD, mixed HL, scoliosis, arachnodactyly, ectopia lentis, cardiovascular abnormalities.
• Osteogenesis Imperfecta - AD, fragile bones, blue sclera, CHL secondary to otosclerosis or ossicular fracture.
• Alport's - AD, SNHL begining @ age 10, renal failure. Hearing improves with renal transplant.
• Crouzon's - AD, CHL in >50% secondary to EAC atresia or ossicle malformation.
• Treacher-Collins - aka mandibulofacial dysostosis, AD, hemifacial asymmetry, CHL secondary to EAC stenosis or ossicular malformation.
• Goldenhar's - AR, colobomas, epibulbar dermoids, CHL.
• Jervell-Lange-Nielson - AR, congenital SNHL, prolonged QT interval, sudden death before adolescence.
• Hurler's - AR, mixed HL, abnormal mucopolysaccharide deposits in tissue, corneal opacity.
• Hunter's - Sex-linked version of Hurler's.
• Pendred's - AR, U-shaped audiogram, euthyroid goiter.
• Usher's - AR, vestibular symptoms common, deaf at birth, retinitis pigmentosa (blind by age 20).
  
  
• AUTOSOMAL RECESSIVE = P.H.U.G.J. = Pendred, Hurler, Usher, Goldenhar, Jervell-Lange-Neilson
• CHL = O.G.A. = Osteogenesis Imperfecta, Goldenhar, Apert

VESTIBULAR DISEASE

Utricle - activated by linear acceleration

Acoustic Neuroma (Schwannoma) - Originates from superior vestibular nerve, CNVII displaced anteriorly at IAC. Accounts for 80% of CP-angle tumors.

Otosclerosis - Fluoride may help

Benign Positional Vertigo - rotatory, fatiguable nystagmus, +Dix-Hallpike, Rx: Epley, Singular neurectomy

Labyrinthine Nystagmus - fast AND slow component. Central Nystagmus is usually pendular (without fast/slow component).

Ampullo- or Utriculopedal flow is stimulatory in Lateral SCC, but Ampullofugal flow is stimulatory in posterior and superior SCC.

Meniere's Disease

• Crisis of Tumarkin - loss of extensor strength, falling with Vertigo
• Lermoyez - Improved hearing after vertigo

TEMPORAL BONE FRACTURE

Longitudinal - 80%

• Commonly conductive HL 2' to perfed TM or ossicular chain dysruption
• 20% injure CN VII, usually at labyrinthine segment

Transverse - 20%

• 50% injur CN VII, usually at geniculate ganglion
• Often 2' to occipital force

Middle Ear CSF Leaks - Oval window or round window leaks most commonly

• Hyrtl's Fissure - (usually infants) opening just anterior/inferior to round window leading to subarachnoid space near CN IX ganglion.

NEUROTOLOGIC ANATOMY

Anatomy of the Intratemporal Facial Nerve

VII - The Facial Nerve
G1 - First Genu, at the Geniculate Ganglion
G2 - Second Genu
CT - Chorda Tympani
TM - Tympanic Membrane
m = Malleus
i = Incus
C = Cochlea
SSCC = Superior Semicircular Canal
PSCC = Posterior Semicircular Canal

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Internal Auditory Canal from medial aspect

BB = Bill's Bar (bony)
TC = Transverse Crest, aka Falciform Crest (bony)
FN = Facial Nerve (also shown is Nervus Intermedius)
SVN = Superior Vestibular Nerve inntervates superior & horizontal canals & utricle
IVN = Inferior Vestibular Nerve to posterior canal and saccule
CN = Cochlear Nerve

In Radiology, we describe this as "Seven-Up and Coke (Cochlear) Down" follow this link for a picture: http://rad.usuhs.mil/medpix/medpix_image.html?mode=image&imageid=16779&topic_id=2255&quiz=no#top

• Type I 95%; 10 fibers to 1 inner hair cell, bipolar
• Type II 5%; 1 fiber to 20 outer hair cells, monopolar
• Inner Hair Cells 20%; afferent.
• Outer Hair Cells 80%; efferent. Sensitive to trauma

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Cochlea in cross section

SV = Scala Vestibuli contains perilymph
SM = Scala Media contains endolymph
ST = Scala Tympani contains perilymph
RM = Reissner's Membrane
BM = Basilar Membrane
VASC = Stria Vascularis - generates +80-100mV potential in endolymph of Media
LIG = Spiral Ligament
LIMB = Spiral Limbus contains inner and outer hair cells
SG = Spiral Ganglion - cochlear nerve fibers located in modiolus of cochlea