Gerard J. Gianoli, MD, FACS The Ear and Balance Institute Baton Rouge, Louisiana

Transcription

1 Gerard J. Gianoli, MD, FACS The Ear and Balance Institute Baton Rouge, Louisiana

2 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

3 January 1998, my first case

4 First reported by Minor in March of 1998 as a cause for pressure or sound-induced vertigo

5 Congenital/Developmental Anomaly Arachnoid Granulations Fracture through SSC roof

6 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:

7 Postnatal development of bone overlying superior canal 24 wks gest. 2 mths 4 mths 10 mths

8 Thickness of bone overlying superior canal increases with age during infancy

9 Incidence of Bilaterality is approx. 50%

10 Multiple Tegmen Dehiscences 80% vs. 20% Encephaloceles Geniculate Ganglion dehiscence 53% vs. 5%

11 Dehiscence

12 SSCD

13 Geniculate Ganglion Dehiscence

14 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

15 Otologic Mimicker Patulous Eustachian Tube Otosclerosis Perilymphatic Fistula Meniere s Disease BPPV

16 Third Mobile Window Theory

17 Third mobile window

18

19 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

20

21 Stage I - Asymptomatic Congenital or Developmental Anomaly

22 Stage II Sup. Canal Syndrome Minor s Syndrome Conductive Hearing Loss Increased Compliance Increased Pressure Weakened RW/OW

23 Stage III Meniere s Syndrome Increased Pressure Prolonged Vertigo SNHL, MHL RW/OW Rupture

24 Stage IV End Stage Increased Pressure Repeated Fistulization Progressing to: Profound SNHL Canal Paresis

25 Diagnosis History Physiologic Testing Imaging Need all three elements for diagnosis

26 Audiometry Impedance Testing Electrocochleography VEMP VNG Rotational Studies Posturography Platform Fistula Test TMD

27 Normal Supranormal Bone Scores Low Frequency up-sloping conductive gap Correlates with size of dehiscence Sensorineural Hearing loss Mixed Loss

28 Normal Tympanometry Normal Acoustic Reflexes

29 When abnormal, often very elevated SP/AP ratio Revert to normal after repair

30 Abnormally sensitive Reduced threshold Elevated magnitude of response Reduction in response with repair

31 Spontaneous Nystagmus Vertical-Torsional Positional Nystagmus Non-BPPV Dix-Hallpike BPPV Calorics Hyperfunction Hypofunction Fistula Test Valsalva Test Tullio s Test Oscillator Test

32

33 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

34

35 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.

36 Normal Increased Gain Reduced Gain with Asymmetry

37 Normal Abnormalities on SOT 5 and 6 Abnormal Platform Pressure Test

38 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

39 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

40

41 No treatment Activity modification Treatment of medical disorders Diuretics? Surgery PE tube RW/OW reinforcement Deafferentation Occlusion of SSC Resurfacing of SSC

42 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?

43 Middle Fossa Floor Arcuate Eminence (SSCD) Temporal Lobe Dura

44 Carved Calvarial Bone

45 Superior Semicircular Canal Dehiscence before repair After repair with calvarial bone and HA bone cement Patency of Superior SCC maintained

46 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

47 Resolution/Improvement Autophony Vertigo/Dizziness Hearing generally unchanged

48 SSCD is a common pathology SSCD has a multitude of clinical presentations SSCD is treatable SSCD should be evaluated thoroughly prior to intervention