an almost understimated realm Dr. Dieter Goettmann Stuttgart University Medical Centers Groningen, Nijmegen

 LVAS is a syndrom  Sensorineural hearing loss  Sudden  Fluctuating  Progressive  Imaging subsidary

E.Pernkopf: Atlas der topographischen Anatomie des Menschen, Bd.IV,München 1960, Tafel 162

 Endolymphatic sac  Extraosseus part  Intraosseus part  Commonly interpretated as the endoymphatic duct  Preductal  Endolymphatic duct  Small & short  Alsmost never dilatated

Intraosseus Part External Aperture of Vestibular Aqueduct Extraosseus Part of Endolymphatic Sac

Unique extracellular fluid  High potassium: 157 mM (CSF: 3.1 mM)  Paramagnetic  Low sodium: 1.3 mMol (CSF: 149 mM)  Low calcium: mM (Perilymph mM)  High electric Potential: 85 mV (CSF: 0mV)  Endocochlear potential  Low flow rate Wangemann, P. and Schacht, J. (1996) Cochlear homeostasis. In: P. Dallos, A.N. Popper and R.R. Fay (Eds) The Cochlea. Handbook of Auditory Research. Vol. 8, Springer, pp

MR?CT + Soft tissue -- - Spatial resolution + - Scan time+ - Endolymph, Sac, Duct + (Borders) - Position jugular bulb +

 Pre-formed  Becoming symptomatic lately

Duct * "funnel"-shape of the extraosseus portion of the endolymphatic sac

Sep. 2008Sep. 2009

 Changes in size and/or delineation of the endolymphatic duct  Clue: Sclerosis of surrounding bone  Fuzzy, hypoattenuated border

 Superior Semicircular Canal Dehiscience  Fenestration or thinned bony layer of the superior semicircular canal 1  Vestibular symptoms evoked by  Sound  Pressure applied to the external auditory canal  Frequency (path., n=1000) 2  Complete defect (fenestration) 0.5 %  4/5 superior petrosal sinus  Thinned < 0.1 mm: 1,4 % 1.LB Minor, D Salomon, JS Zinreich, DS Zee: Sound- and/or Pressure-Induced Vertigo Due to Bone Dehiscience of The Superior Semicircular Canal. Arch Otolaryngol 1998(124): JP Carey, LB Minor, GT Nager: Dehiscience or Thinning of Bone Overlying Superior Semicircular Canal in a Temporal Bone Survey. Arch Otolaryngol 2000(126):

 Superior petrosal sinus groove  Partial volume effect Superior Petrosal Sinus Groove

 Irregular shape

 High flow in the jugular bulb may cause excavation (wall shear stress -> remodelling)  Sometimes it reaches structures of the inner ear  Posterior semicircular canal  Endolymphatic sac Posterior SCC Endolymphatic sac

 Fuzzy margins, not to be explained by partial volume effects  Sclerosis Endolymphatic sac (intraosseus segment) Normal Margin

 Sensorineural hearing loss  Conductive hearing loss  Tinnitus  Pulsatile  Often not well differentiated by the Otologist  E.g. „progressieve sensoneural hearing loss with a conductive component“

 Think of it  In the field of SNHL, CT can provide more answers than MRI  Size (ax.) of the intraosseus part  Arbitrary: <= 1,5 mm, <= size f posterior SCC  Deliniation  Fuzziness  Environmental sclerotic reaction  Jugular bulb  High? High riding?  Divertikel? (coronal plane)  Arrosion of the inner ear?

 LVAS is a syndrome with enlargement being just one feature  In adults it may have different imaging features than in children e.g.  Enlargement of the endolymphatic sac  May be progressive  Surrounding sclerotic reaction  Dehiscience of a semicircular canal  Clinical correlation w. evoked vestibular symptoms essential  Jugular bulb variants  Jugular Bulb Diverticulum  High riding Jugular Bulb  Understanding of physiology is reconsidered. As is pathophysiology.