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Official Description

Craniotomy with elevation of bone flap; for selective amygdalohippocampectomy

© Copyright 2025 American Medical Association. All rights reserved.

Common Language Description

The procedure described by CPT® Code 61566 involves a craniotomy, which is a surgical operation where a portion of the skull is removed to access the brain. Specifically, this procedure includes the elevation of a bone flap for a selective amygdalohippocampectomy (SAH), a surgical technique aimed at treating mesial temporal lobe epilepsy that has not responded to conventional medical therapies. The amygdalohippocampectomy targets specific areas of the brain, namely the amygdala and hippocampus, which are critical in the generation of seizures associated with this type of epilepsy. The procedure can be performed using various approaches, including the subtemporal approach, which is conducted beneath the temporal lobe; the transcortical approach, which involves passing through the cortex and gray matter; or the transsylvian approach, which entails a wide dissection of the sylvian fissure. During the operation, the patient's head is secured using a three-pin fixation device to ensure stability. An incision is made in the temporal area to expose the temporalis fascia, which is then opened and separated from the periosteum. The skin and muscle flap are retracted laterally to allow access to the skull, where a bone flap is elevated using burr holes and a craniotome. The dura mater, a protective membrane covering the brain, is opened and flapped anteriorly to provide access to the brain cortex for the selective amygdalohippocampectomy. This procedure is critical for patients suffering from intractable epilepsy, as it aims to remove the epileptogenic tissue while preserving surrounding functional brain areas. The detailed steps involved in the procedure ensure that the surgical team can effectively address the underlying causes of the patient's seizures while minimizing potential complications.

© Copyright 2025 Coding Ahead. All rights reserved.

1. Indications

The procedure described by CPT® Code 61566 is indicated for the treatment of mesial temporal lobe epilepsy that is unresponsive to medical therapy. This condition is characterized by recurrent seizures originating from the temporal lobe, often associated with significant morbidity and impaired quality of life. The selective amygdalohippocampectomy aims to alleviate seizure activity by removing the affected brain tissue, specifically targeting the amygdala and hippocampus, which are known to play a crucial role in seizure generation.

  • Mesial Temporal Lobe Epilepsy This condition is often resistant to pharmacological treatments, necessitating surgical intervention to improve seizure control and overall patient outcomes.

2. Procedure

The procedure begins with the patient positioned appropriately and their head secured using a three-pin fixation device to ensure stability throughout the surgery. An incision is made in the temporal area to expose the temporalis fascia, which is then opened and separated from the periosteum. The skin and muscle flap are retracted laterally to provide access to the skull. A bone flap is elevated using burr holes and a craniotome, allowing the surgical team to access the underlying dura mater. The dura is then opened and flapped anteriorly to expose the brain cortex, which is essential for performing the selective amygdalohippocampectomy.

  • Step 1: Incision and Exposure An incision is made in the temporal area, and the temporalis fascia is opened and separated from the periosteum. The skin and muscle flap are retracted laterally to expose the skull.
  • Step 2: Elevation of Bone Flap A bone flap is elevated using burr holes and a craniotome, providing access to the dura mater covering the brain.
  • Step 3: Opening the Dura The dura is opened and flapped anteriorly, allowing access to the brain cortex for the selective amygdalohippocampectomy.
  • Step 4: Identification of Intraventricular Anatomy The surgical team identifies the intraventricular anatomy, including the dural floor of the middle fossa, pial boundary overlying the suprasellar cistern, and other critical structures.
  • Step 5: Resection of Parahippocampal Gyrus The parahippocampal gyrus is resected medially and posteriorly while preserving the mesial pial border, allowing for mobilization of the hippocampus laterally into the cavity.
  • Step 6: Continuation of Resection The resection continues anteriorly and posteriorly to the level of the tectal plate, with the removal of the targeted tissue.

3. Post-Procedure

At the conclusion of the selective amygdalohippocampectomy, bleeding is controlled using electrocautery and/or gelfoam to minimize the risk of postoperative complications. The dura is then closed, and the elevated bone flap is plated back into position. The temporalis muscle is reapproximated, and the scalp is closed in layers to ensure proper healing. Post-procedure care includes monitoring for any signs of complications, managing pain, and providing appropriate follow-up to assess the patient's recovery and seizure control.

Short Descr REMOVAL OF BRAIN TISSUE
Medium Descr CRANIOTOMY SELECTIVE AMYGDALOHIPPOCAMPECTOMY
Long Descr Craniotomy with elevation of bone flap; for selective amygdalohippocampectomy
Status Code Active Code
Global Days 090 - Major Surgery
PC/TC Indicator (26, TC) 0 - Physician Service Code
Multiple Procedures (51) 2 - Standard payment adjustment rules for multiple procedures apply.
Bilateral Surgery (50) 0 - 150% payment adjustment for bilateral procedures does NOT apply.
Physician Supervisions 09 - Concept does not apply.
Assistant Surgeon (80, 82) 2 - Payment restriction for assistants at surgery does not apply to this procedure...
Co-Surgeons (62) 1 - Co-surgeons could be paid, though supporting documentation is required...
Team Surgery (66) 0 - Team surgeons not permitted for this procedure.
Diagnostic Imaging Family 99 - Concept Does Not Apply
APC Status Indicator Inpatient Procedures, not paid under OPPS
Type of Service (TOS) 2 - Surgery
Berenson-Eggers TOS (BETOS) P1G - Major procedure - Other
MUE 1
CCS Clinical Classification 9 - Other OR therapeutic nervous system procedures

This is a primary code that can be used with these additional add-on codes.

69990 Addon Code MPFS Status: Restricted APC N ASC N1 PUB 100 CPT Assistant Article 1Microsurgical techniques, requiring use of operating microscope (List separately in addition to code for primary procedure)
58 Staged or related procedure or service by the same physician or other qualified health care professional during the postoperative period: it may be necessary to indicate that the performance of a procedure or service during the postoperative period was: (a) planned or anticipated (staged); (b) more extensive than the original procedure; or (c) for therapy following a surgical procedure. this circumstance may be reported by adding modifier 58 to the staged or related procedure. note: for treatment of a problem that requires a return to the operating/procedure room (eg, unanticipated clinical condition), see modifier 78.
AS Physician assistant, nurse practitioner, or clinical nurse specialist services for assistant at surgery
GC This service has been performed in part by a resident under the direction of a teaching physician
Date
Action
Notes
2004-01-01 Added First appearance in code book in 2004.
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