Differential Diagnosis in Neurology

5.8. Cranial Nerve VIII

• Anatomy (General)
  • Auditory nerve:
    • Afferents of the cochlea
  • Vestibular nerve
  • Afferents from the saccular and utricular macula
    • Sense linear acceleration
  • Cristae of the semicircular canals:
    • Sense angular acceleration

Anatomy and Physiology of the Auditory Pathways

• Hair cells of the organ of Corti (first order neurons) stimulated by sound:
  • Cochlear apex senses low tones; hair cells at the base; base high tones:
  • Spiral ganglion of the cochlear nerve
  • Comprise the cell bodies of the first order neurons
• Rosenthal's canal
• Afferents of the spiral ganglion neurons contact inner (majority) and outer hair cells of the cochlea
• Activation of hair cells depolarizes the spiral ganglia neurons whose efferents synapse in the ventral cochlear nucleus (cochlear nerve)
• Cochlear nerve projects and synapses with:
  • Dorsal cochlear nucleus
  • Anteroventral and posteroventral nuclei of the cochlear complex
  • Dorsal components of the complex process afferents from "high frequency" basal cells; ventral neurons process afferent from the "low-frequency" apical cells
  • Dorsal and ventral cochlear nuclei project to the contralateral brainstem nucleus of lateral lemniscus
  • Dorsal acoustic striae:
    • Intermediate acoustic stria (dorsal part of the ventral cochlear nucleus)
    • Ventral acoustic stria (part of trapezoid body)
  • Lateral lemniscus projects to the inferior colliculus and medial geniculate nucleus
  • Ventral cochlear nucleus synapses with the superior olivary nucleus: reticular formation and the nucleus of the trapezoid body
  • Medial geniculate body (afferents from the inferior colliculus):
    • Low frequency fibers-synapse on the apical lateral areas
    • High frequency afferent fibers synapse in the medial portion of the nucleus
  • MGB (geniculotemporal fibers) project to lamina IV of the primary auditory cortex (BA 41) and association areas of BA 42 . High tones terminate medially and low tones laterally.
    • Core system for audition:
      • Central nucleus of the inferior colliculus
      • Components of the medial geniculate
      • Primary auditory cortex
      • Direct auditory pathway
      • Tonotopic organization
    • Alternative auditory projection system:
      • Pericentral region of the inferior colliculus (IC)
      • Non laminated MGB neurons
      • BA 42 (secondary auditory cortex)
      • Less tonotopic organization

Anatomy of the Vestibular System

• Monitors angular and linear accelerations of the head
• Accelerations are transduced into action potentials in the membranous labyrinth (utricle, saccules and, semicircular canals)
• Linear acceleration registered by:
  • Macules of the utriculus and sacculus
• Angular acceleration registered by:
  • Cristae in the ampullae of the semicircular canals
• Horizontal head movements: stimulates the utricle linearly; tilting activates the sacculus
• Activation of cristae or macules discharges neurons in the vestibular ganglion of scarpi whose afferent fibers are the vestibular nerve:
  • Anterior, horizontal semicircular canals (SCC) and the utricle comprise the superior portion of the vestibular nerve
  • Posterior SCC and sacculus comprise the inferior portion of the nerve
  • Afferents to the vestibular nerve:
    • Superior nucleus (Bechterew) SCC
    • Lateral nucleus (Dieter) macules (utriculus and sacculus); comprises the vestibular spinal tract
    • Medial nucleus (Schwalbe) SCC
    • Inferior (Roller) macula (utriculus and sacculus)
  • Vestibular efferents:
    • MLF; superior nucleus is ipsilateral; other nuclei efferents are contralateral
    • Medial vestibular tract:
      • Excitation or inhibition of the cervical and upper thoracic levels of the contralateral spinal cord
    • Lateral vestibulospinal tract:
      • LVN; ipsilateral spinal cord; cervical cord afferents project to the posteroventral part of the nucleus; lumbosacral to the dorsocaudal areas of the nucleus
      • Excitatory projections to extensor trunk muscles; antigravity axial muscles; afferents from the utriculus "anti-gravity detection"
    • Cerebellum receives afferents from:
      • Inferior and medial nuclei
      • Ipsilateral floccular nodular lobe (receives LVN projections)
      • Uvula; fastigial nucleus (receives LVN projections
    • Reticular formation receives afferents from VN and projects to:
      • Lateral reticular nucleus
      • Nucleus reticularis pontis caudalis

Topography of Clinical Symptoms

• Decreased perception of tones or speech:
  • Lesion central to the oval window
• Cochlear deficit (sensory); perception of sound
• Cochlear nerve or nuclei or central pathways; perception of sound
• Sensorineural loss:
  • Greater difficulty with high pitched sounds
  • Loss of speech discrimination > pure tone deafness
  • Tinnitus (varies in pitch and intensity):
    • Paroxysmal or continuous
    • More frequent with external middle ear disease than central lesions
• Low roaring-cochlear hydrops (Méniére's)
• High pitched; presbycusis; VIII nerve tumor
• Pulsatile tinnitus:
  • Glomus jugulare tumor
  • Intracranial or cervical aneurysm
  • Increased intracranial pressure (unilateral tinnitus)
  • Middle ear congenital defects
  • Arteriovenous malformation

Miscellaneous Causes of Tinnitus

• Gaze evoked tinnitus (after removal of tumors of CPA); presents with saccadic movements pursuit or vestibular induced movements
• TMJ disease
• Labyrinthitis
• Brainstem lesions
• High cardiac output
• Palatal myoclonus (clicking in association with the myoclonic jerks)

Localization of Lesions Causing Sensorineural Deafness

• Cerebral lesions (BA 41, BA 42, BA 22) :
  • No complete deafness even with bilateral lesions of the cortex
  • Unilateral lesion:
    • Subtle hearing impairment with unilateral lesion
    • Difficulty locating sounds
    • Predominantly posterior temporal lesions or bilateral temporal lesions; pure word deafness (inability to comprehend spoken language) with normal auditory acuity; reading, writing, naming and comprehension of non-language sounds are intact
    • Bilateral lesions of the auditor cortex:
      • Cortical deafness
      • Generalized auditory agnosia
      • Selective auditory agnosia
      • Pure word deafness
      • Amusia
      • Depressed temporal analysis of sound

Irritative Lesion of the Temporal Cortex

• Simple auditory hallucinations (tinnitus) > complex hallucinations (voice or music)
• BA 42 and BA 22 cause more hallucinations than BA 41
• Temporal lobe seizures have both acoustic and vertiginous auras (dizziness one of the commonest TLE auras)

Brainstem Lesion

• Lesions above cochlear nucleus there is no clinical hearing loss
• Bilateral hearing loss:
  • Trapezoid body (stroke or hemorrhage)
  • Pons (stroke or hemorrhage)
  • Midbrain tegmentum (hemorrhage, tumor)
  • Pineal and midbrain tumor:
    • Central stem deafness of Brunner (pressure on the isthmus acusticus); bilateral
  • Lower midbrain or rostral pontine tegmentum lesions cause:
    • Auditory hallucinations (release type)
    • Clear sensorium
    • Hearing loss
  • Brainstem auditory hallucinosis with lower pontine tegmental hemorrhage

Peripheral Nerve Lesions

• Cochlear lesion:
  • Deafness
  • Tinnitus
  • High frequency hearing loss
• Causes:
  • Basal skull fracture
  • Syphilis/bacterial infection
  • Streptomycin/neomycin/gentamicin
  • AICA aneurysm
  • CPA tumors

Acoustic Neurinoma

• General features:
  • Origin: vestibular portion of VIIIth nerve in the IAC
  • Unilateral high pitched tinnitus
  • Progressive sensorineural hearing loss
  • Early loss of speech discrimination
  • Less than 10% have sudden deafness
  • Vertigo, dizziness, ipsilateral unsteadiness (vestibular nerve involvement)
  • V, VI, VII (weakness, loss of taste anterior 2/3 of tongue, Hitselberger sign (numbness of external auditory canal)
  • Decreased corneal reflex (if anterior to the IAC)
  • Hydrocephalus
• Anterior extension of the tumor:
  • V (facial pain, decreased corneal reflex)
  • VIth nerve weakness
• Posterior inferior extension:
  • IX dysphagia, absent pharyngeal reflex
  • X hoarseness
  • XI trapezius, sternocleidomastoid muscle weakness

Vertigo

Peripheral Causes:

• Short duration
• Severe, paroxysmal
• Tinnitus
• Hearing loss (may be associated)
• Nystagmus (horizontal/rotary; contralateral; decreased by visual fixation)
• Romberg (fall to the affected side); subjective environmental twirl, past pointing-to the side of the lesion; fast component of nystagmus to the opposite side

• Canal paresis (total loss of horizontal SCC):
  • Ipsilateral head rotation cause compensatory refixation saccades
• Bilateral vestibular paresis:
  • Head movement-dependent oscillopsia (movement of the visual environment only with head movement)
• Positional vertigo (induced by head position):
  • Benign positional vertigo:
    • Degeneration of the macula of the otolith; obstruction of endolymph floor
    • Lesions of the PSCC (otoconia from degenerating utricular macula attach to the cupula of the posterior SCC)
    • Differential diagnosis of cupulolithiasis:
      • Trauma
      • Infection (Hs)
      • Labyrinthine fistula
      • Ischemia
      • Demyelinating disease
      • Posterior fossa tumor
      • Arnold–Chiari malformation
  • Benign positional vertigo (BPPV):
    • Induced nystagmus:
      • Latency 2–15 seconds
      • Fatigue (lasts less than 10 seconds)
      • Torsional nystagmus
      • No associated cochlear or central symptoms
      • Vertigo (less than 60 seconds)
      • Upright position: rebound nystagmus to the opposite side
      • Lying in lateral position may cause protracted nystagmus
      • May have long course (years); one exacerbation after initial remission
      • Habituates (lesions with continued repositioning)
  • Central vertigo:
    • Short latency
    • No fatigue
    • No habituation
    • Vertigo absent or mild (less than 60 seconds)
    • Nystagmus:
      • Direction changing greater than fixed
      • Induced by several head positions
    • Associated CNS signs
  • Maturational vertigo:
    • Induced on rising; turning over in bed prior to rising
    • Disorders in which vertigo and nystagmus are prominent

Differential Diagnosis of Peripheral Vestibulopathy

Vestibular neuronitis:

• Acute severe vertigo; associated with nausea and vomiting
• Absent calorics on the affected side
• Self-limited ; lasts 7–10 days
• No cochlear symptoms or other neurologic signs
• Unrelated to head position
• May reoccur

Acute Labyrinthitis

• Vertigo, nausea and vomiting
• Tinnitus
• Hearing loss
• Follows: bacterial or viral labyrinthitis; aminoglycosides; loop diuretics

Aberrant Branch of AICA Compresses the VIIIth Nerve

• Constant positional vertigo
• Severe nausea
• Tinnitus

Méniére's Disease

• Episodic severe vertigo
• Fluctuating sensorineural hearing loss
• Fullness or pressure sensation in the ear
• Bilateral in 30–40% of patients
• Endolymphatic hydrops; increased volume of endolymph
• Roaring tinnitus
• Attacks: minutes to hours
• Between attacks: dysequilibrium noted in some patients
• Hearing loss low tones (<3K Hz)

Variants of Méniére's

• Cochlear Méniére's:
  • Vertigo is absent
• Vestibular Méniére's:
  • Severe vertigo
  • Hearing loss and tinnitus are later features
• Tumarkins otolithic catastrophe:
  • Severe episodic vertigo
  • Loss of muscle tone; patient falls to the ground
  • No loss of consciousness
• Medical conditions with severe episodic vertigo:
  • Congenital syphilis (bilateral disease)
  • Viral and bacterial labyrinthitis
  • Hyperlipidemia
  • Diabetes mellitus
  • Labyrinthine otosclerosis
  • Hypothyroidism
  • Ramsay Hunt (HZ of geniculate ganglion):
    • Vesicular eruption of the external auditory meatus
    • Peripheral facial paralysis
    • Vertigo
    • Hearing loss
  • Chronic ear infection
  • Putative autoimmune etiology
  • Cardiac insufficiency:
    • Cardiac arrhythmia:
      • Tachyarrhythmia with decreased stroke volume
      • Presyncopal feeling
      • Visual loss (closing in from the side)
      • Fading out of hearing
      • "Light headed" or dizzy
    • Congestive heart failure
    • Aortic stenosis
    • Carotid sinus hypersensitivity

Hematologic Disease

• Anemia:
  • Polycythemia vera
  • Waldenström's macroglobulinemia (hyperviscosity)
  • IgM monoclonal gammopathies
• Hypoglycemia:
  • Dizziness and faintness
  • Cold sweat
  • Convulsion (sugar less than 40 mg/dl)
• Hypothyroidism:
  • VIII nerve hearing loss
  • Cerebellar ataxia
  • Vertigo
• Hyperventilation:
  • Perioral paresthesia
  • Tingling fingers (paresthesias)
  • Fasciculations
  • Usually described as light headedness
• Multiple sensory deficit syndrome:
  • Elderly patients; occurs during walking
  • Visual impairment (cataracts; macular degeneration)
  • Proprioceptive sensory loss (neuropathy)
  • Cervical spondylosis
  • Depression
• Central vertigo characteristics:
  • Prolonged duration
  • Concomitant brainstem and or cerebellar signs
  • Auditory symptoms are less prominent
  • Vertigo less severe and continuous
  • May lack nystagmus, vertigo, deviation of the body

Vascular Vertigo

• Vertebrobasilar insufficiency:
  • Vertigo and dizziness moderately severe
  • Deafness or hearing loss is rare
  • Associated often with brainstem, cerebellar, cranial nerve or long tract signs
  • Ischemia of central auditory pathways or labyrinth (internal auditory or subarcuate arteries)
• Lateral medullary syndrome (Wallenberg's); PICA:
  • Vertigo, dizziness, nausea and vomiting
  • IXth, Xth nerve involvement
  • Rotary nystagmus to side of the lesion; overshooting of saccades
  • Ipsilateral ataxia
  • Ipsilateral Vth nerve decreased sensation; loss of sensation below the clavicle to temperature and pinprick (L > A)
• Lateral branch infarction may just have vertigo and dizziness (PICA)
• Labyrinthine stroke:
  • Occlusion of the internal auditory artery (origin is AICA)
    • Superior vestibular artery: vertigo, nausea and vomiting
    • Common cochlear artery: deafness
• Bickerstaff's migraine:
  • Vertebrobasilar ischemia
  • Tingling of the hands
  • Dizziness, dysarthria, ataxia
  • Short loss of consciousness
• Subclavian steal syndrome:
  • Severe stenosis of the subclavian artery prior to the origin of the vertebral artery
  • Dizziness, dysarthria, diplopia
  • Occurs during continued overhead use of the right arm
  • Rarely symptomatic
• Cerebellar infarction or hemorrhage
• BPV may occur secondary to labyrinthine ischemia
• Dolichoectasia of the vertebral, basilar and AICA arteries
• AICA or PICA aneurysm with distal emboli or vasospasm

Vertigo from Head or Cervical Trauma

• Inner ear concussion
• Fracture of the temporal bone with labyrinthine or VIII nerve damage
• Uncovertebral joint (cervical spine) or cervical plexus injury (unequal afferent information to the vestibular nuclei)

Syndromic Deafness (Selected)

• Méniére's disease
• Susac's disease
• Wolfram (DIDMOAD)
• Norrie's
• Romano ward
• LEOPARD
• Albinism deafness syndrome
• Voigt–Koyanagi–Harada
• Pendred
• Usher
• Alstrom
• Roger (TRMA)
• Otodental
• Brachia-oto-renal
• CHARGE
• Large Vestibular aqueduct
• Vohwinkel
• SAPHO
• Wolf–Hirschhorn
• Jervell Lange Nielsen
• Perrault
• Treacher–Collins
• Waardenburg
• DiGeorge
• Wildervanck
• Fountain
• Bing–Nell

Méniére's (discussed above) Disease

Susac's Syndrome:

• Retinal vascular lesion
• Sensorineural hearing loss
• Stroke

Wolfram Syndrome (DIDMOAD); Familial or Sporadic

• Diabetes insipidus
• Optic atrophy
• Deafness
• Urinary tract (anomalies)
• Abnormalities of endocrine glands
• MRI:
  • Absence of high signal in the posterior pituitary
  • Shrinkage of optic nerves, chiasm, tracts
  • Atrophy of hypothalamus
  • Atrophy brainstem and cerebellum
  • Atrophy of the cortex
  • High signal in SN (substantia nigra)

Norrie's Syndrome (Atrophia Oculi Congenita)

• X-linked recessive
• Bilateral deafness at birth (20–25% of blind males)
• Phthisis bulbi
• Dementia or psychosis in 25%
• Pseudotumor of the retina
• Lens, corneal opacities

Differential Diagnosis

• Retinoblastoma
• Retrolental fibroplasia
• Toxoplasmosis
• Falciform detachment of the retina
• Juvenile retinoschisis
• Sex linked microphthalmia
• Sex linked cataract and congenital retinal detachment

Romano–Ward Syndrome

• AD
• Long – QT
• Sudden death from tachyarrhythmia
• HERG gene

Leopard Syndrome

• Lentigines
• Ocular hypertelorism
• Mental and growth retardation
• Deaf mutism

Albinism with Deafness

Voigt–Koyanagi–Harada

• White forelock
• Dementia
• Cerebellar degeneration
• Uveitis
• Recurrent meningitis
• VIII nerve involvement

Pendred Syndrome

• AR; 7.5–10/100,000; 7q 22–31
• Goitre (thyroid dysfunction variable)
• Sensorineural hearing loss
• Malformation of inner ear

Usher's Syndrome

• AR 3.4/100,000
• Congential bilateral sensorineural hearing loss
• Progressive visual loss from retinitis pigmentosa
• Type 1 (USH1); 14q; 11q; 10q, 21q:
  • Congenital deafness
  • Absent vestibular function
• Type II (USH2); 1q:
  • Moderate-to-severe hearing loss (congenital)
  • Normal vestibular function
• Type III (USH3); 3q:
  • Progressive loss
  • Normal vestibular function
• Myo7A gene (encodes myosin VII A); USH1B
• USH2A phenotype (laminin is encoded)

Alström's Syndrome

• AR; French Canadians; North Africans
• Retinal pigment degeneration
• Neurogenic deafness
• Infantile obesity
• Hyperlipidemia
• Non-insulin dependent diabetes mellitus
• Chromosome 2p12–13

Roger (Thiamine Responsive Megaloblastic Anemia; TRMA) Syndrome

• AR; chromosome 1q23.2–1q23.3
• Megaloblastic anemia
• Diabetes mellitus
• Sensorineural deafness
• Responds to megadoses of thiamine
• SLC19AZ gene on 1q23.2–23.3 encodes thiamine transporter 1 (THTR-1)

Otodental Syndrome

• AD
• Bulbous canines; globe shaped posterior teeth; agenesis of maxillary premolars
• High frequency sensorineural hearing loss
• Abnormalities of deciduous and permanent dentition

Branchio-Otic-Renal Syndrome (BOR)

• AD; BOR gene at chromosome 8q13
• Preauricular pits branchial fistulas
• Renal anomalies
• Hearing loss
• Some families: branchial anomalies, preauricular pits, and hearing loss; no renal anomalies; some families branchial and renal anomalies with no hearing impairment

CHARGE Syndrome

• Coloboma (79%)
• Heart malformations (85%)
• Choanal atresia (57%)
• Growth-mental retardation (100%)
• Genital anomalies (34%)
• Ear anomalies (91%)
• Deafness (62%)
• Semicircular canal hypoplasia
• Cranial nerve palsy
• Facial anomalies
• Neonatal brainstem deficits
• Polytopic development field defect involving the neural tube and neural crest cells

Large Vestibular Aqueduct Syndrome

• Progressive sensorineural hearing loss

Cogan's Syndrome

• Ocular inflammation
• Vestibulo-auditory dysfunction
• Vasculitis (includes abdominal and mesenteric arteries)

Vohwinkel Syndrome

• Mutilating keratoderma
• Papular and honeycomb keratoderma
• Constriction of digits (autoamputation)
• Starfish acral keratoses
• Sensorineural deafness
• Mutation in connexin 26 (CX26 gene); encodes portions of intercellular gap junctions
• Nonconservative mutation of D66H in CX 26

SAPHO Syndrome

• Synovitis
• Acne
• Palmoplantar pustulosis
• Hyperostosis
• Osteitis
• Diffuse sclerosing osteomyelitis of the mandible; inflammatory spread from the TMJ to the cochlea (sudden deafness)

Perrault Syndrome

• Ovarian dysgenesis
• Deafness

Treatcher–Collins (Mandibulofacial Dysostosis)

Wildervanck Syndrome:

• Variant of Klippel–Fiel
• Retraction of eye ball
• Deaf mutism

Wartenberg Syndrome

• AD
• Lateral displacement of medial canthus
• Approximation of eye brows
• White forelock
• Heterochromia aurides
• Absence of organ of Corti
• Atrophy of spiral ganglion

Alport Syndrome

• Congenital renal disease
• Marked stria atrophy; mild secondary neural degeneration

Cockayne Syndrome

• Retinitis pigmentosa
• Sensorineural deafness
• Cerebellar ataxia
• Peripheral neuropathy
• Microcephaly; dwarfism
• Kyphosis
• Flexion deformity
• Loss of subcutaneous fat
• Photosensitivity to UV (ultra violet) light
• Anhidrosis

Hallgren Syndrome

• Retinitis pigmentosa (RP)
• Profound congenital deafness
• Ataxia
• Mental retardation

Laurence–Moon Biedl Syndrome

• RP
• Sensorineural hearing loss
• Mental retardation
• Obesity
• Polydactyly
• Hypogonadism

Refsum's Disease

• Intermittent neuropathy
• Cataracts
• Phytanic acid elevation
• Ichthyosis
• Short stature
• Increased CSF protein

Retinitis and hearing Loss

• OPCA
• Juvenile and adult onset lipidoses

Optic Atrophy, Hearing Loss and Peripheral Neuropathy

• Friedreich's ataxia (uncommon)

Hearing Loss and Optic Atrophy

• Sylvester syndrome (AD):
  • Optic atrophy, ataxia, progressive hearing loss
• Nyssen Van Bogaert syndrome:
  • Opticocochleodentate degeneration
• Rosenberg-Chutorian syndrome:
  • Optic atrophy, polyneuropathy, sensorineural hearing loss

Rare Associations of Hearing Loss

• Spinal muscular atrophy
• Fascio scapular humoral dystrophy
• Roussy–Levy syndrome
• Myotonic dystrophy

Brown-Vialetto-Van Laere Syndrome

• Pontobulbar palsy with deafness
• Familial
• Bilateral nerve deafness
• Motor components of VII; IX–XII; rarely III, V, VI involved
• Severe loss of axons of the auditory and vestibular nerves

Non-Syndromic Hereditary Hearing Loss

• Mitochondrial genetic disease:
  • MELAS
  • Mitochondrial 3243t RNA A (leu) A to G mutation
    • Pigmentary retinal dystrophy
    • Defective retinal pigment epithelial
    • Cells of rod and cone photoreceptors are deficient
    • A3243G 0.5 to 2% of diabetics
    • Deafness
  • MERFF
  • PEO
  • Kerne–Sayre syndrome
• Identified Genes/Chromosomal Loci/Genetic Associations:
  • CX26 (mutated 50% of all recessive deafness)
  • Myosin 7A – usher type 1B (identified with syndromic/nonsyndromic hearing loss)
  • X-Linked deafness type 3-POU3FH gene
  • DFNA6 chromosome 4p 16.3 (progressive low frequency hearing loss)
  • Mitochondrial 12S r RNA deficit
  • Enlarged vestibular aqueduct; nonsyndromic hearing loss; same 7q 31 locus as Pendred syndrome
  • X-Linked cochlear degeneration
  • Autosomal dominant cerebellar atrophy-type I
  • Familial spastic paraparesis (complicated)
  • Autosomal dominant recurrent VIII nerve deafness
  • Familial vestibulopathy
  • Familial amyloidosis type IV
  • Late onset peroxisomal deficiency
  • X-Linked deafness
  • CADASIL
  • AD osteogenesis imperfecta
  • Hereditary sensory autonomic neuropathy
  • X-Linked motor-sensory neuropathy type II
  • Trisomies of D and E
• Tumors Affecting the VIII Nerve:
  • Carcinomatosis of the meninges
  • Leukemia
  • Lymphoma
  • Acoustic Schwannoma (NFI or sporadic)
  • Meningioma
  • Epidermoid (primary and secondary)
  • Metastasis
  • Exophytic glioma
  • Pinealoma (dysgerminoma; pineocytoma)
  • Ependymoma
  • Malignant melanoma (metastatic)
  • Neurofibromatosis (type II; bilateral acoustic neuroma)
  • Intravascular malignant lymphoma
• Infections:
  • Tuberculosis
  • Cryptococcus
  • Aspergillosis
  • Deep fungal infection
  • HIV
  • CMV
  • Purulent bacterial meningitis
  • EBV
  • Vestibular neuronitis
  • Cysticercosis
  • Histoplasmosis
  • Coccidioidomycosis
• Drugs/Toxins/Physical Agents:
  • Cis-platinum
  • Aminoglycosides
  • Superficial siderosis
  • Furosemide diuretics (loop diuretics)
  • Zidovudine
  • Dideoxyadenosine
  • Streptomycin
  • Interferon gamma 1
  • Depakote
  • X-RT
  • Increased ICP
  • Midbrain trauma
  • Trauma skull
  • Alcohol
  • Lead
  • Mercury
• Bone Disease:
  • Paget's disease
  • Fibrous dysplasia (Albright's syndrome)
  • Synchondrosis of the skull
  • Osteogenesis imperfecta
  • Congenitally small IAC
• Vestibular Disease:
  • Bing–Neel (hyperviscosity syndromes)
  • Hypothyroidism
  • Syphilis
  • Autoimmune (putative); AIDP; CIDP
  • Drug (cis-platinum; streptomycin)
  • Cupulolithiasis (displaced otoconia)
  • Trauma (petrous and skull fractures)
  • Perilymphatic fistula
  • Vestibular hemorrhage (trauma)
  • Hypertrophic VII nerve compression of the VIIIth nerve (IA Meatus)
• Defects in development:
  • Aplasia:
    • Complete absence of the otic capsule and VIIIth nerve; thalidomide ingestion
    • Incomplete development of the bony and membranous labyrinth; dysgenesis of the spiral ganglion
    • Membranous cochleosaccular dysplasia of the VIIIth nerve in the porous acoustics; 20% of patients
• Trauma:
  • Blunt trauma:
    • Transverse or longitudinal fracture (relations to the long axis of petrous bone)
    • Longitudinal fractures:
      • More common than transverse
      • Usually no VIIIth nerve damage
    • Transverse fracture:
      • Anteroposterior trauma
      • Roof of the internal auditory meatus in fractured
      • Total deafness and severe vertigo; 40–50% of patients; concomitant VIIth nerve paralysis
    • Blunt head trauma with temporal bone fracture:
      • Concussion of the inner ear
      • Concomitant secondary neural degeneration
    • VIIIth nerve injury from commercial and sports diving
• Infection:
  • Blood borne infection:
    • Reaches the inner ear by invasion of the endolymphatic system
    • Meningoencephalitis:
      • Invasion along the nerves and vessels of the internal auditory meatus
    • Streptococcus pneumonia, meningococcus and haemophilus influenzae:
      • Direct invasion of the labyrinth with subtotal destruction of sensory and neural elements
      • Total vestibular destruction may cause oscillopsia if any vestibular function remains; central compensation occurs with no vestibular symptoms but profound hearing loss
    • Syphilitic labyrinthitis:
      • Most common cause of hearing loss in syphilitic patient
    • Borrelia burgdorferi (Lyme's):
      • Cochlear and vestibular involvement
    • Petrositis (chronic middle ear infection):
      • Gradenigo's syndrome: otitis media, VI as it crosses the petrous bone; pain behind the ipsilateral eye (V nerve ganglia in Meckel's cave). Vertigo and hearing loss due to erosion of the bony labyrinth or the VIIIth nerve in its bony canal.
    • Pseudomonas aeruginosa (malignant external otitis):
      • Debilitated; severe diabetic or renal failure patients
      • Invades the junction of the cartilaginous and osseous portion of the external auditory canal to invade adjacent bones

Viral Infection

• Viruses may damage the cochlea greater than the VIIIth nerve
• Also, meningoencephalitis directly invades along the nerves and blood vessels (Herpes Zoster and mumps)
  • Ramsay Hunt:
    • Deep burning ear pain
    • Several days after onset: vesicular eruption of the external auditory canal and cochlea
    • Concomitantly or 1–2 days following vesicular rash, hearing loss and vertigo occurs; may involve the VIIIth nerve directly
• Infection of Scarpa's ganglia demonstrated with HS, rubella and reovirus
• Vestibular neuronitis:
  • Affects patients who are:
    • 30–60 years of age
    • Sudden vertigo involving one ear that lasts for 1–3 weeks
    • Nystagmus is opposite the involved ear
    • No hearing loss; no associated neurologic signs
    • Recovery in many months; may recur
    • Superior and ampullary branches of the vestibular nerve are involved; normal cochlea

Disorders of the Temporal Bone

• Otosclerosis:
  • Disease of the bony labyrinth
  • Immobilization of the stapes
  • Compression by otosclerotic foci of cochlear neural elements
• Paget's disease:
  • Hearing loss is usually bilateral
  • Sensorineural deficit; may have conductive deficit
  • Vestibular symptoms usually progressive, but may be episodic
• Fibrous dysplasia:
  • Compression of the VIIIth nerve
• Osteopetrosis:
  • VIIth and VIIIth nerve compression may be early symptoms
  • Conductive defect:
    • Narrowing of the external auditory meatus
    • Encroachment of bones of the middle ear on the ossicles
  • Sensorineural deficit (compression of the cochlear nerve in the IAC)
• Recessive osteosclerosis (Van Buchem syndrome or hyperostosis corticalis generalisata):
  • Hyperostosis; skull, ribs, clavicle, long bones and pelvis
  • VII and VIII nerve palsy in 50% of patients
  • Encroachment of bone in the neural foramina
• Hyperostosis cranialis interna:
  • Hyperostosis and osteosclerosis of the calvaria and base of the skull (only)
  • AD inheritance
  • Recurrent VII nerve palsy, decreased vision, hearing and vestibular function
  • Cranial nerve foraminal encroachment