Gerard J. Gianoli, MD, FACS The Ear and Balance Institute Baton Rouge, Louisiana
SSCD is defined anatomically as the absence of bone between the SSC and the middle fossa dura PSCD is a defect of the PSC bone between PSC and posterior fossa dura Less common
January 1998, my first case
First reported by Minor in March of 1998 as a cause for pressure or sound-induced vertigo
Congenital/Developmental Anomaly Arachnoid Granulations Fracture through SSC roof
Histological Studies (n=1000) 2% of temporal bones have thinning or dehiscence overlying superior canal sps Carey et al. Arch Otolaryngol Head Neck Surg 2000;126:137-147
Postnatal development of bone overlying superior canal 24 wks gest. 2 mths 4 mths 10 mths
Thickness of bone overlying superior canal increases with age during infancy
Incidence of Bilaterality is approx. 50%
Multiple Tegmen Dehiscences 80% vs. 20% Encephaloceles Geniculate Ganglion dehiscence 53% vs. 5%
Dehiscence
SSCD
Geniculate Ganglion Dehiscence
All age groups Typical onset of symptoms in adulthood Probably under-diagnosed in childhood Most Characteristic Symptoms Strain-induced vertigo Tullio s Phenomenon Autophony Hear beat, Eye movement, Voice, Respiration, Heel- Strike, Joint movement
Otologic Mimicker Patulous Eustachian Tube Otosclerosis Perilymphatic Fistula Meniere s Disease BPPV
Third Mobile Window Theory
Third mobile window
Congenital Pathology with onset of symptoms in adulthood Asymptomatic patients Patient response to OW/RW reinforcement Does not explain all of the symptomatology, e.g. Meniere s spells
Stage I - Asymptomatic Congenital or Developmental Anomaly
Stage II Sup. Canal Syndrome Minor s Syndrome Conductive Hearing Loss Increased Compliance Increased Pressure Weakened RW/OW
Stage III Meniere s Syndrome Increased Pressure Prolonged Vertigo SNHL, MHL RW/OW Rupture
Stage IV End Stage Increased Pressure Repeated Fistulization Progressing to: Profound SNHL Canal Paresis
Diagnosis History Physiologic Testing Imaging Need all three elements for diagnosis
Audiometry Impedance Testing Electrocochleography VEMP VNG Rotational Studies Posturography Platform Fistula Test TMD
Normal Supranormal Bone Scores Low Frequency up-sloping conductive gap Correlates with size of dehiscence Sensorineural Hearing loss Mixed Loss
Normal Tympanometry Normal Acoustic Reflexes
When abnormal, often very elevated SP/AP ratio Revert to normal after repair
Abnormally sensitive Reduced threshold Elevated magnitude of response Reduction in response with repair
Spontaneous Nystagmus Vertical-Torsional Positional Nystagmus Non-BPPV Dix-Hallpike BPPV Calorics Hyperfunction Hypofunction Fistula Test Valsalva Test Tullio s Test Oscillator Test
CSF Loss of bony canal integrity SSC (ASC) less frequently PSC A Third Window effect is evoked by CSF pressure change Often stimulated upon change in position, particularly to recumbent
Intensity DH Dn (either R or L) DH Up (Often not seen) 10 sec Take home point: In ASC or PSC dehiscence, both the R and L DH Dn tests evoke the same nystagmus picture.
Normal Increased Gain Reduced Gain with Asymmetry
Normal Abnormalities on SOT 5 and 6 Abnormal Platform Pressure Test
MRI Chiari Malformation Type I Posterior Fossa Malformation Rule out other etiologies Meningioma CT scan Confirm Diagnosis Bilaterality? Concomitant Middle Fossa Anomalies LVAS PSCD Tegmen Defects Encephaloceles Geniculate Ganglion Dehiscence
Not all CT scans are equal Need: High resolution Sub millimeter slices (<0.6 mm) Bone algorithm Direct Coronal and Axial slices Reconstructions Plane of SSC Right angle plane of SSC Radial Slices of SSC
No treatment Activity modification Treatment of medical disorders Diuretics? Surgery PE tube RW/OW reinforcement Deafferentation Occlusion of SSC Resurfacing of SSC
Occlusion Loss of SSC function Invasive to inner ear higher risk of inner ear damage Difficulty with assessment of persistent vertigo Recurrence loose plug syndrome Resurfacing Preserves SSC function Less invasive/risk to inner ear CT scan easily assesses success of repair in cases of persistent vertigo Technically more challenging?
Middle Fossa Floor Arcuate Eminence (SSCD) Temporal Lobe Dura
Carved Calvarial Bone
Superior Semicircular Canal Dehiscence before repair After repair with calvarial bone and HA bone cement Patency of Superior SCC maintained
Hearing Loss Persistent Dizziness/Vertigo Loose Plug Syndrome BPPV Failure of resurfacing PLF Chemical Labyrinthitis? BioSet Delayed Facial Palsy CSF Leak and other Intracranial Complications
Resolution/Improvement Autophony Vertigo/Dizziness Hearing generally unchanged
SSCD is a common pathology SSCD has a multitude of clinical presentations SSCD is treatable SSCD should be evaluated thoroughly prior to intervention