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2.9: Subtotal Petrosectomy

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    17703
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    OPEN ACCESS ATLAS OF OTOLARYNGOLOGY, HEAD & NECK OPERATIVE SURGERY

    SUBTOTAL PETROSECTOMY

    Tashneem Harris & Thomas Linder


    Subtotal petrosectomy involves complete exenteration of all air cells of the temporal bone (middle ear and mastoid). It includes the following cell tracts: retrosigmoid, retrofacial, antral, retrolabyrinthine, supralabyrinthine, infralabyrinthine, supratubal and pericarotid cells. Only a few cells in the petrous apex are left behind. The otic capsule is either kept intact or removed (subtotal petrosectomy with or without removal of the otic capsule). The external auditory canal is closed as a blind sac and the cavity obliterated with abdominal fat and a temporalis muscle flap. Complete removal of disease is important before obliterating the cavity.

    Indications

    1.png

    Figure 1: Chronically discharging mastoid cavity

    • Chronic otitis media when there is no possibility of hearing reconstruction and one wishes to attain a dry, safe ear (Figure 1)

    2.png

    Figure 2: Audiogram showing dead left ear

    • Chronic otitis media in a completely deaf ear (Figure 2)

    3.png

    Figure 3: Type B temporal paraganglioma

    • Middle ear tumors (Figure 3)
    • CSF leaks which may be traumatic, iatrogenic or (rarely) spontaneous
    • Supralabyrinthine and/or infralabyrinthine cholesteatoma

    4.png

    Figure 4: Transverse temporal bone fracture of right ear involving vestibule

    • Transverse temporal bone fracture (Figure 4)
    • In combination with another neurotologic procedure e.g. Transotic and Infratemporal fossa approaches “Types A, B or C”

    5.png

    Figure 5: Subtotal petrosectomy and cochlear implant

    • Cochlear or middle ear implantations where an open cavity has previously been performed (Figure 5)
    • Cochlear implantation in the case of congenital cochlear dysplasia where there is a high risk of a CSF gusher
    • Osteoradionecrosis of the temporal bone

    Preoperative management

    Imaging

    • Patients undergoing subtotal petrosectomy require High Resolution CT (HRCT) scan prior to surgery
    • Refer to the preoperative CT checklist in the chapter on Mastoidectomy and epitympanectomy
    • If patients have had previous surgery, it is particularly important to pay attention to structures which may have been exposed at the primary surgery e.g. facial nerve, sigmoid sinus and dura

    Audiogram

    • Review audiograms to decide whether it is necessary to remove the stapes superstructure or if it should be preserved
    • If there is no possibility of hearing reconstruction e.g. a dead ear, then the stapes superstructure may be removed
    • If hearing is reasonable then it may be wise to preserve the stapes superstructure as the patient may decide to have a semi-implantable hearing aid (Vibrant Soundbridge) fitted in the future.

    Perioperative antibiotics: Amoxicillin with clavulanic acid

    Operative site

    • The patient’s hair is shaved for a distance of 7 cm above and behind the hairline
    • The inferior abdominal quadrant and suprapubic areas are shaved and prepared for harvesting a fat graft

    6.png

    Figure 6: Positioning of patient

    Positioning: The patient lies supine with the head turned away from the surgeon (Figure 6)

    Facial nerve monitoring: Avoid longacting muscle relaxants as the facial nerve should be monitored intraoperatively

    Surgical Steps

    Skin Incision

    7.png

    Figure 7: Postauricular S-shaped incision

    • A postauricular S-shaped incision is made from the temporal region to 1 cm below the mastoid tip (Figure 7)
    • The superior part of the incision above the temporal line is only made at the end of the procedure when a temporalis muscle flap is needed

    Mastoid periosteal flap

    • This flap is used as a 2nd layer in the closure of the external auditory canal and is therefore left attached to the cartilaginous canal
    • Using a surgical scalpel with a #10 blade, the skin is reflected anteriorly remaining superficial to temporalis fascia and muscle

    8.png

    Figure 8: Mastoid periosteal flap

    • The anteriorly based periosteal flap is developed measuring about the size of the surgeon’s finger. (Figure 8)
    • It must be long enough to achieve closure of the external canal especially in the case of previous surgery with an open cavity where the periosteal tissue may be of poor quality

    Blind sac closure of external auditory canal

    Transection of the auditory canal

    • The periosteal flap is elevated until the bony-cartilaginous junction of the external auditory canal is reached

    9.png

    Figure 9: Incision in ear canal

    • An incision is made from 6-12 o’clock in the posterior auditory canal (Figure 9)
    • To transect the anterior portion of the canal, use a curved clamp to find the tragal cartilage
    • A large curved artery clamp is then used to develop a plane anterior to the tragal cartilage separating the parotid from the cartilage

    10.png

    Figure 10: Safely transecting anterior wall of ear canal

    • Holding the curved clamp in this position, a #15 blade is used to safely transect the anterior canal by cutting onto the curved clamp. This avoids injury to the facial nerve (Figure 10)

    Eversion of auditory canal skin

    • Ocular magnifying loupes are useful for this step

    11.png

    Figure 11: Elevating skin of external canal

    • The skin of the cartilaginous canal is elevated for 1 cm from the cut margin with tympanoplasty scissors to facilitate eversion of the canal (Figure 11)
    • It is important that the skin of the external canal is not breached. To avoid this, direct the curve of the tympanoplasty scissors towards the cartilage
    • It may be difficult to find the correct plane, especially if a previous open mastoidectomy with a wide meatoplasty was performed

    12.png

    Figure 12: Placing stay sutures

    13.png

    Figure 13: Stay sutures

    • Two 2-0 vicryl stay sutures are placed at 6 and 12 o’clock. These are placed as 2 purse string sutures with the free ends on the inside of the canal (Figures 12, 13)

    14.png

    Figure 14: Everting skin of the ear canal

    • A curved artery clamp is passed through the canal from externally and applied to each of the free ends of the two stay sutures. Tension is applied to the stay sutures to evert the canal skin (Figure 14)

    15.png

    Figure 15: Oversewing canal

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    Figure 16: Oversewn canal

    • The tragus is retracted with a skin hook and the skin edges are oversewn with 4-0 vicryl suture (Figures 15, 16)

    17.png

    Figure 17: Oversewing the sac with the periosteal flap

    • The periosteal flap is folded back as a 2 nd layer to the blind sac closure of the external auditory canal (Figure 17). It is sutured to the cartilage of the external auditory canal with 2-0 vicryl

    Removal of lateral external auditory canal skin

    • The skin of the bony external canal is elevated with a Key raspatory

    18.png

    Figure 18: Removing skin of ear canal

    • This skin cuff is removed with tympanoplasty scissors (Figure 18)

    Removal of medial external auditory canal skin

    • A microraspatory and small strip of adrenaline gauze is used to elevate the remnants of the external auditory canal skin to the annulus
    • The middle ear is entered at the posterior tympanic spine and the annulus is elevated. The short process of malleus, chorda tympani and incudostapedial joint are now visible
    • Chorda tympani is divided with a large Bellucci scissors
    • The incudostapedial joint is separated with a 45° 1.5 mm hook
    • The malleus is cut at its neck with a malleus nipper
    • Tensor tympani tendon is cut with a large Bellucci scissors
    • The tympanic membrane (with handle of malleus attached) is now be removed along with the incus and head of malleus

    Mastoidectomy

    • It is important that all mastoid cells are exenterated, and no mucosa is left behind as this can potentially form mucocoeles
    • Structures like dura, sigmoid sinus and facial nerve must be skeletonized, not exposed
    • Using a mastoid raspatory elevate the soft tissues off the mastoid
    • Free the sternocleidomastoid muscle from its insertion into the mastoid tip
    • Place a 2-0 silk stay suture from the edge of temporalis muscle to its fascia to expose the area above the temporal
    • Next proceed as for open mastoidoepitympanectomy (see chapter on mastoidectomy)
    • After performing an open mastoidoepitympanectomy the additional cells are removed to complete the subtotal petrosectomy
    • The stapes superstructure is removed using crurotomy scissors to cut the anterior and posterior crura
    • The inferior surface of the external ear canal can be lowered to the level of the hypotympanum
    • It is important to review the CT scan to confirm again that the jugular bulb is not high-riding before skeletonizing the jugular bulb
    • The pericarotid cells are exenterated by first approaching the anterocarotid cells. The carotid is recognized by its whitish color beneath the bone. The carotid is not infrequently dehiscent at its bend medial to Eustachian tube
    • The mastoid tip may be left in place, but is drilled down to the level of the digastric ridge

    19.png

    Figure 19: Mastoid cavity with all cell tracts having been exenterated

    • Retrofacial, retrosigmoid, retrolabyrinthine, supralabyrinthine, infralabyrinthine, and supratubal cells are all exenterated. Figure 19 shows the mastoid cavity once all the cell tracks have been exenterated

    Technical points

    • When drilling in the supralabyrinthine segment a diamond drill is used in reverse when operating on the right ear to avoid injuring the facial nerve
    • The mucosa of the middle ear can be removed by using the microraspatory and scraping the mucosa with a small cotton ball, taking care not to sublux the stapes superstructure if left intact

    Obliteration of Eustachian tube

    • The internal carotid artery is followed superiorly to the medial wall of the Eustachian tube (watch out for a dehiscent carotid at this point!)
    • The mucosa of the bony Eustachian tube is removed as far as the isthmus with a 2 mm/3 mm diamond burr

    20.png

    Figure 20: Eustachian tube obliterated with bone wax

    • At this point the remaining mucosa is coagulated with bipolar forceps and the Eustachian tube is obliterated with bone wax (Figure 20)

    21.png

    Figure 21: Eustachian tube obliterated with bone wax

    • Using a cottonoid, the bone wax may be pushed into the orifice of the Eustachian tube with a suction tip. The tip of the microraspatory is directed away from the carotid (Figure 21)
    • A temporalis muscle musculofascial graft is used as an additional seal of the orifice by placing it lateral to the bone wax

    Technical points

    • The tensor tympani muscle can be dissected out of its semicanal by drilling its lateral surface and reflecting it anteriorly with a microraspatory into the protympanum and the Eustachian tube orifice
    • Bone wax is then placed over this so that the muscle lies sandwiched between two layers of bone wax, thus obliterating the Eustachian tube

    Obliteration of Operative Cavity

    22.png

    Figure 22: Abdominal fat

    • The middle ear cleft is obliterated with abdominal fat harvested from the lower quadrant of the abdomen (Figure 22)
    • It is important to achieve meticulous hemostasis as a hematoma of the abdominal wound is the most common complication of subtotal petrosectomy
    • A suction drain is placed in the abdominal wound
    • The abdominal wound is closed in layers using subcutaneous 3-0 vicryl and monocryl 3-0 or nylon 3-0 to skin
    • With osteoradionecrosis of the temporal or chronic infection it is advisable not to use abdominal fat to obliterate the cavity. Rather use only temporalis muscle

    Transposition of temporalis muscle

    • The skin incision is extended superiorly above the temporal line to expose the temporalis muscle
    • Remaining in a plane above the temporalis fascia, the skin and soft tissue edges are undermined
    • Using two skin rakes, the assistant retracts the skin edges for adequate exposure
    • The posterior 2/3 of the temporalis muscle is mobilized by creating a flap using a diathermy knife
    • To facilitate mobilization and transposition of the temporalis flap over the mastoid cavity, a small inverted V shaped incision is made at the base of the temporalis muscle

    23.png

    Figure 23: Temporalis flap and abdominal fat in petrosectomy defect

    • The muscle flap is rotated inferiorly over the cavity and sutured to the sternocleidomastoid muscle and soft tissues of the occiput with 2-0 vicryl (Figure 23)

    24.png

    Figure 24: Additional fat placed in defect

    • Inevitably the fat used to obliterate the cavity will atrophy; therefore, more fat is placed in the cavity once the temporalis muscle has been sutured to the soft tissues via the superior pocket created by the transposed temporalis flap (Figure 24)

    Wound Closure

    • A 3 mm suction drain is placed under the scalp over the squamous part of the temporal bone and not over the mastoid cavity
    • The wound is closed in layers with 2-0 vicryl sutures subcutaneously and skin clips
    • A compression bandage is applied

    Postoperative care

    • Antibiotics (amoxicillin with clavulanic acid) are continued for one week postoperatively
    • The drain is left in place until the drainage is less than 10mL/24hrs.
    • If the surgery was done for a CSF leak, then the drain is removed on the first postoperative day
    • The abdominal drain is removed when the drainage is less than 10mL/24hrs
    • Clips/sutures are removed after 10 days
    • The resorbable vicryl sutures within the external ear canal are removed at 4 weeks

    Long-term follow-up

    Imaging

    • Where subtotal petrosectomy is performed for chronic otitis media, CT scans are routinely performed after one year and then again at 3 years
    • In cases of previous cholesteatoma, a diffusion weighted non-EPI MRI would detect recurrent disease

    Auditory rehabilitation

    This depends on the status of hearing of opposite ear, the degree and type of hearing loss and cochlear function. The options are a bone anchored hearing aid (BAHA) if the inner ear function has been preserved of the ipsilateral or contralateral ear; active middle ear implant (e.g. Vibrant Soundbridge) where there is good cochlear reserve; or a cochlear implant (bilateral deafness).

    References

    1. Fisch U, Mattox D, eds. Microsurgery of the Skull Base. Stuttgart,Germany: Georg Thieme Verlag, 1988.
    2. Linder T, Schlegel C, DeMin N, van der Westhuizen S.Active Middle Ear Implants in Patients Undergoing Subtotal Petrosectomy: New Application for the Vibrant Soundbridge Device and Its Implication for Lateral Cranium Base Surgery. Otol Neurotol. 2008; 30:41-7

    Acknowledgements

    This guide is based on the text by Professor Fisch (Microsurgery of the Skull Base) and personal experience of Professor Linder, as well as course materials for the lateral skull base course conducted annually by Professors Fisch and Linder at the Department of Anatomy, University of Zurich, Switzerland.

    Authors

    Tashneem Harris MBChB, FCORL, MMed, Fisch Instrument Microsurgical Fellow
    ENT Specialist
    Division of Otolaryngology
    University of Cape Town
    Cape Town, South Africa
    harristasneem@yahoo.com

    Thomas Linder, M.D.
    Professor, Chairman and Head of Department of Otorhinolaryngology, Head, Neck and Facial Plastic Surgery
    Lucerne Canton Hospital, Switzerland
    thomas.linder@ksl.ch

    Editor

    Johan Fagan MBChB, FCS(ORL), MMed
    Professor and Chairman
    Division of Otolaryngology
    University of Cape Town
    Cape Town, South Africa
    johannes.fagan@uct.ac.za


    2.9: Subtotal Petrosectomy is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Open Access Atlas of Otolaryngology, Head & Neck Operative Surgery.