SUBTEMPORAL APPROACH.pptx,Anatomy , medical

Anatomy is the study of the structure of the human body.
Physiology, in contrast, focuses on how these body parts function together.
The human body is composed of several major organ systems that work in concert.
The circulatory system is responsible for transporting blood, oxygen, and nutrients throughout the body.

1. SUBTEMPORAL APPROACH Harshal Vijay Desai MDE2002

2. Why? Allows to access a wide range of areas for treating various pathologies, including tumors and vascular issues, with less invasiveness than some traditional methods. Particularly useful for deep-seated conditions and offers benefits like a shorter operative time and avoids extensive skull base resection

3. Where? Middle fossa floor Anterior basal cisterns Upper clivus

4. When? Resection of mid to posterior intraparenchymal tumor. Resection of convexity temporal lobe tumors Access to mid hippocampal lesions Access to lateral thalamus tumors Access to basal cisterns through transcortical, transventricular, transchoroidal pathway.

5. What? Middle fossa meningiomas Small acoustic tumors Trigeminal schwannomas Low-lying basilar caput/upper basilar artery aneurysms Upper petroclival meningiomas

6. Pre-op Location of vein of Labbe and its drainage site into the transverse sinus should be estimated. Displacement of other arterial and venous structures along the medial tentorium should be defined. Potential need for a combined approach to tumors with both supratentorial and infratentorial extensions should be planned pre-op. Mannitol (1g/Kg) should be administered during skin incision. A lumbar drain for most patients, regardless of tumor size, in order to minimize the risk of temporal lobe retraction injury during intradural or extradural elevation of the lobe.

7. Subtemporal craniotomy Appropriate head position is paramount for surgery on deep skull base lesions. Patient’s head position should direct the surgeon to the region of interest through a path that allows: 1. Adequate exposure of lesion 2. Minimizes brain retraction 3. Affords flexible working angles 4. Enables comfortable body posture for surgeon during procedure.

8. Patient position Patient is frequently placed in the supine position if the patient’s neck is supple. In lateral position: 1. Neck is relatively rigid 2. Older and heavy-set patients 3. Patient has history of significant cervical spondylosis, this dictates the need for a lateral position. Head is then tilted ~20 degrees towards the floor for gravity retraction to mobilize the temporal lobe away from the middle fossa.

9. Skin incision Exact location and size of the lesion will determine the corresponding skin incision. Smaller lesions that are withing the superior or middle temporal gyri are amenable to linear incisions. Whereas large subtemporal lesions benefit from a horseshoe-shaped incision. For lesions that require access to the anterior temporal pole, a small reverse questions mark incision would be appropriate.

10. Craniotomy Placing a generous single burr hole just above the root of zygoma Penfield dissector to mobilize the dura away from the inner table of calvarium in preparation for craniotomy. If an extradural approach to middle fossa is planned, it’s essential to avoid early injruy to the dura in order to protect the lobe during extradural subtemporal dissection and petrosectomy.

11. If the dura is adherent to the inner skull bone, then olace numerous burr holes. Lumbar drain is used to remove ~30-40cc of CSF gradually. Drainage facilitates dissection of the dura from calvarium and reduces risk of dural tear. Craniotome is then used to complete the craniotomy. In case of subtemporal operative corridor, the craniotomy should be as close to the middle fossa floor. Identify landmark: upper edge of the zygoma. Floor is oblique and slopes superiorly from ant. to post. Therefore, inferior edge of the craniotomy should be only slightly above the level if the zygoma.

12. The craniotomy in relation to the root of zygoma is evident. Most often, the inferior edge of the craniotomy leaves a strip of overhanging bone, obscuring path toward the middle fossa. Subsequently, a Leksell Rongeur may be used to remove this overhanging bone until the edge of the craniotomy is at the level of the floor. Handheld drill further assists with this task.

13. Closure A watertight dural closure primarily or secondarily using a piece of dural allograft. Adipose tissue with its globular texture is one of the best barriers against CSF leakage. Before placement of the adipose grafts, all air cells must be meticulously waxed. In case of subtemporal skull base exposures that require removal of the tumor-infiltrated dura and bone, strips of adipose tissue are placed across the dural opening to seal the dural defect.

14. Alternatively, a vascularized muscle flap prepared from the posterior aspect of the temporalis muscle may be rotated to fill the defect within the bone or dura. This latter method is used during repeat operations for patients whoe have previously undergone radiation. Any additional mastoid and temporal air cell are rewaxed. Finally, the bone flap is replaced and the scalp is closed in anatomic layers.

15. Post-op Patient is admitted to the ICU for neurologic and vlood pressure monitoring and pain control. Frquent and careful neurologic exams are paramount because temporal lobe hematomas can occur due to lobar retraction injury or venous drainage compromise, leading to rapid BS compression. Lumbar drainage may be continued if there is high suspicion of CSF leak. Due to manipulation of the temporal lobe, the use of prophylactic antiepileptic meds for atleast a week after is recommended.

16. Pearls and Pitfalls During positioning, tilting the patient’s head toward the floor is a key maneuver to maximize the use of gravity retraction and obtain appropriate subtemporal exposure. The upper edge of zygoma is a good landmark for locating the level of the middle fossa floor. Removal of the overhanging inferior edge of the craniotomy is important for preparing an obstructed operative trajectory toward the middle fossa floor. The location of the vein of Labbe should be estimated pre-op. Dural opening and extradural temporal lobe elevation should be adjusted for protection of this vital venous structure.