External Approach to the Paranasal Sinuses

4. Chronic frontal sinusitis

5. Frontal sinus obliteration

– Comminuted and/or displaced posterior table fractures

– Cerebrospinal fluid leak

– Severe frontal outflow tract obstruction

6. Reduction of frontal sinus fractures

7. Type 4 frontal cells

8. Neoplasm extending to anterior skull base or ethmoid sinus

9. CSF leak repair

• Contraindication to open approach to the frontal sinus:

1. Pathology amenable to endoscopic approach

2. Metastatic malignant disease

3. Massive brain involvement

4. Cavernous sinus involvement

Surgical Procedures

Surgical Landmarks to the Frontal Sinus

• Supraorbital foramen

• Superomedial rim of the orbit

• Anterior lacrimal crest

Mapping the Frontal Sinus

• Intraoperatively, mapping of the frontal sinus can assist in identifying the boundaries of the sinus for safe entry into the sinus cavity.

• Mapping of the frontal sinus can be achieved with several methods:

1. Image-guided navigation systems: used intraoperatively to identify entry points to the frontal sinus

2. Transnasal illumination with endonasal endoscopes

3. Frontal sinus mini-trephination and drilling a pilot hole in the anterior table; endoscopes are introduced through the mini-trephination for transillumination and identification of the frontal sinus cavity

4. Removal of anterior frontal sinus table and exposure of the sinus cavity

5. Conventional 6-foot Caldwell standard radiograph templates:

– Templates of the frontal sinus are formed and used

– Intraoperatively to demarcate the margins the frontal sinus

– Anterior table (Figure 27–1)

Bicoronal Flap Incision

• Done externally behind the hairline

• Incision connects the scalp anterosuperior to the auricles bilaterally

• Dissection of the flap is carried along the incision caudally to the level of supraorbital rim while avoiding injury to the supraorbital neurovascular bundle

• Laterally, the flap is elevated above the temporalis fascia to avoid injury to the frontal branch of the facial nerve (Figure 27–2)

• Dissection plane depends on the surgical objective:

1. If a pericranial flap is planned, dissection is carried in the supraperiosteal plane along the areolar tissue layer of the scalp.

2. Pericranium is incised separately to the level of the bone, then elevated caudally to the supraorbital ridges; the supraorbital neurovascular pedicle is dissected and elevated off the supraorbital notch (Figure 27–3).

3. If a pericranial flap is not required, the initial bicoronal incision is deepened to the level of the bone and dissection is carried in a subperiosteal plane.

• Mapping of the frontal sinus cavity is carried out prior to entry to the cavity using the methods mentioned above.

• Entry into the frontal sinus cavity is achieved by drilling several openings in the anterior table that are then connected using an oscillating saw; the bone is cut circumferentially around the anterior table in order to completely separate it for access.

• If an osteoplastic flap is planned, the anterior table is cut at the superior and lateral margins; an osteotome is then used to divide the intersinus septum, which is then removed using a rongeur and the anterior table is down-fractured at the supraorbital rim, being attached by the pericranium inferiorly.

• The frontal sinus pathology is then addressed.

Advantages: wide exposure of the frontal bone and the superior orbital rim, preservation of supraorbital neurovascular pedicle

Disadvantages: scar in patients with male pattern baldness, extensive dissection

Gull-Wing Incision (Full Brow Incision)

• Bilateral supraorbital incisions connected medially at the glabella (see Figure 27–2)

• Similar dissection planes and entry to the frontal sinus cavity as the bicoronal approach; however, the superior branches of the supraorbital pedicle are sacrificed, resulting in forehead anesthesia above the incision.

Advantages: limited dissection compared to bicoronal incision

Disadvantages: forehead anesthesia/paresthesia, poor cosmesis

Forehead Crease Incision

• Indicated mainly for patients with male pattern baldness to avoid scalp scars.

• Incision is typically placed along a deep mid forehead rhytid (see Figure 27–2).

• Dissection and entry to the frontal sinus is similar to bicoronal incision.

• If a pericranial flap is planned, then the pericranium can be preserved at the incision site and the forehead skin dissected superiorly to the level of the hairline, where the pericranium is incised and reflected as an inferiorly based flap.

• This approach can be combined with endoscopy, either endonasally or through the anterior table of the frontal sinus.

Advantages: avoids scalp scar, preserves supraorbital neurovascular bundle

Disadvantages: forehead scar, limited exposure

Frontal Sinus Trephination

• The simplest open approach to the frontal sinus

• Indications: biopsy of frontal sinus lesions, acute frontal sinusitis with impending complications, adjunct to endoscopic approach

• Procedure:

1. Make a stab incision at inferomedial brow around 1 to 1.5 cm from the midline (Figure 27–4)

2. Soft tissue and periosteum dissection is carried to the level of the bone, sparing the supratrochlear neurovascular bundle.

3. A 4-mm burr is used to enter the inferomedial aspect of the sinus.

4. The frontal sinus opening can be enlarged using a bone rongeur

5. Instrumentation with endoscopes and irrigation using a cannula or biopsy can be taken through the trephine (Figure 27–5).

6. Reconstruction is achieved with approximation of periosteum and soft tissue.

Advantages: minimally invasive, better cosmesis

Disadvantages: limited exposure for any useful frontal sinus surgery as a stand-alone procedure, scar formation

Complications of External Approaches to Frontal Sinus

• Frontal sinusitis

• Frontal osteomyelitis

• Wound dehiscence

• Frontal sinus mucocele/mucopyocele

• CSF leak

• Orbital injury

• Intracranial hemorrhage/injury

• Forehead anesthesia/paresthesia

• Scarring

• Frontal recess stenosis

• Frontalis nerve injury

Frontal Sinus Reconstruction Post External Approach

Primary closure: mainly in frontal sinus trephination and after Lynch procedure where anterior table defect is minimal and non-deforming

Bone graft: for bicoronal and forehead approach; anterior table of the frontal sinus is used as a bone graft; position is secured using miniplates or fixation wires

Local flaps: can be utilized in osteoplastic flaps; the anterior table along with the overlying periosteum is hinged back to the original position; fixation can be achieved with or without fixation wires and plates

Free flaps: microvascular osteocutaneous free flaps indicated for large skull base and frontal bone defects, if previously operated, or if history of irradiation

Soft tissue: sutured primarily

Nasofrontal duct: can be stented using silastic/silicone sheets or polyvinyl chloride endotracheal tubes

Medial canthal ligament: internasal wiring to contralateral medial canthus or frontal plates are placed to stabilize the medial canthal ligament

Jul 20, 2019 | Posted by in OTOLARYNGOLOGY | Comments Off on External Approach to the Paranasal Sinuses
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