Endoscopic Transcanal Ear Anatomy and Dissection Manual
11
6. Study the classification of depth and extension of the sinus tympani. (Fig. 15, 16) 7. Study the shape and depth of the sinus tympani in your specimen. Try to classify (palpate, if necessary) the type of sinus tympani of your specimen as well as the one shown in this manual. (Fig. 10) 8. Observe the ponticulus promontorii and its possible variations. (Fig. 17)
Type A
Type b
Type A
Type C
a
Type B
15 The various types of sinus tympani classified according to depth and extension in relation to the facial nerve. Cochlear promontory (pr); facial nerve (fn); sinus tympani (st)
b
Type C
c 16 Schematic drawing of a ‘Type C’ sinus tympani. The indicates the posterior extension of the sinus tympani with respect to the third portion of the facial nerve (fn). Chordal ridge (cr); chorda tympani nerve (ctn); lateral tympanic sinus (lts);
facial sinus (fs); incus (in); malleus (ma); onticulus (p); pyramidal eminence (pe); p cochlear promontory (pr); posterior sinus tympani (pts); stapedial tendon (st); stapes (s); subiculum (su); round window (rw).
17 The variable morphological appearance of the ponticulus promontorii (p). Ridge ponticulus (Type A); incomplete ponticulus (Type B), bridge ponticulus (Type C). Facial nerve (fn); incus (in); ponticulus (p); pyramidal eminence (pe); posterior sinus tympani (pts); cochlear promontory (pr); stapedial tendon (st); stapes (s); subiculum (su); sinus subtympanicus (ss).