Endolymphatic Sac Surgical Technique

The surgical suite is set up as it is for doing a mastoidectomy, with the bed turned either 90 or 180 degrees. The patient should be positioned with the

Lymph Sacs

FIGURE 24-1 Postauricular incision.

nonoperative ear approximated to the contralateral shoulder. This improves visualization of the sac as it exits the labyrinth, toward the descending segment of the sigmoid sinus. As the endolymphatic sac may be in close proximity to the facial nerve, intraoperative monitoring should be considered.

An incision is made just outside the postauricular crease (Fig. 24-1). Lidocaine with epinephrine (1:100,000 or 1:200,000) may be infiltrated into the soft tissue prior to incision for vasoconstriction. The mastoid periosteum is divided in a cursive T (Fig. 24-2) and elevated to expose the entire mastoid cortex (Fig. 24-3). The cartilaginous ear canal is elevated off of the spine of Henle to allow full visualization of the posterior bony external auditory canal. A complete mastoidectomy is performed and the lateral semicircular canal is exposed (Fig. 24-4). Just posterior to the lateral canal, bone over the posterior semicircular canal is taken down until the latter canal can be appreciated. The endolymphatic sac will generally be apparent just caudal to the posterior canal. The mastoid segment of the facial nerve is identified, leaving a thin layer of bone overlying, as the sac may be medial to the nerve (Fig. 24-5). Failure to recognize the facial nerve may lead to injury on its posterior or medial surface. The sigmoid sinus is skeletonized and followed medially along the posterior fossa, up to the posterior semicircular canal (Fig. 24-6). The eggshell-thin bone over the sigmoid is fenestrated with a diamond bur, creating either an island of bone to remove in

Endolymphatic Sac Removal Surgery

Temporalis 'Temporal line muscle

FIGURE 24-2 The mastoid periosteum is divided in a T fashion.

FIGURE 24-1 Postauricular incision.

Temporalis 'Temporal line muscle

FIGURE 24-2 The mastoid periosteum is divided in a T fashion.

Medial Cortex Vertebra

FIGURE 24—3 The mastoid periosteum is elevated until cortex is completely exposed, including the spine of Henle.

Temporal line

FIGURE 24—3 The mastoid periosteum is elevated until cortex is completely exposed, including the spine of Henle.

Mastoid Antrum
FIGURE 24-4 A mastoidectomy is performed with bone removed in a smooth plane and the deepest point of the dissection over the mastoid antrum.

toto or a slit from which to elevate the remaining bone. Bipolar cauterization of the sigmoid sinus improves visualization of the posterior fossa dura. Bone over the posterior fossa is then taken down, lateral to medial, up to the posterior semicircular

Labyrynthine Tympanic Mastoid
FIGURE 24-5 After completion of the simple mastoi-dectomy, the lateral and posterior semicircular canal (PSCC) and sigmoid sinus are exposed. The mastoid segment of the facial nerve is identified, but left covered with bone.
Labyrynthine Tympanic Mastoid
FIGURE 24-6 The sigmoid sinus and vestibular labyrinth are skeletonized, with creation of an island of bone over the dome of the sinus.

canal and extending inferiorly as much as the sigmoid sinus will allow. The sac may be identified by elevating the dura and sac off the posterior face of the posterior semicircular canal and palpating the bony operculum more anteromedially (Fig. 24-7). The wound is thoroughly irrigated and closed in layers with absorbable sutures. A mastoid pressure dressing is applied. This completes an endolympha-tic sac decompression.

The endolymphatic sac may be opened and a shunt inserted (Fig. 24-8). The value of shunts has been questioned, relative to decompression, as

Mastoid Shunt

FIGURE 24—7 Bone over the sigmoid sinus and posterior fossa cortex is removed up to the posterior semicircular canal. The endolymphatic sac and duct can be confirmed by palpating the operculum medial to the posterior canal.

Endolymphatic Mastoid Shunt SurgeryEndolymphatic Mastoid Shunt Surgery

Stem or shunt placed

FIGURE 24—8 The endolymphatic sac may be incised and a shunt inserted into the sac lumen.

Stem or shunt placed

FIGURE 24—8 The endolymphatic sac may be incised and a shunt inserted into the sac lumen.

shunts typically become encased in fibrous tissue. Presumably this renders the shunt ineffective. The efficacy of endolymphatic sac decompression and shunt are equivalent.

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