General characteristics and indications
This operation is strictly palliative in nature, meaning it does not eliminate the root cause of the disease, but is vital for preventing fatal complications. The primary goal of the surgeon is to create an artificial defect in the bony framework of the skull and the dura mater in a specific area of the vault to relieve high pressure.
The main indications for the procedure include:
- Pronounced increase in intracranial pressure (ICP).
- Presence of inoperable brain tumors causing a mass effect.
- Progressive edema of brain tissue developed as a result of severe traumatic brain injury.
Before starting the surgery, the patient is placed in a specific position: on the left side, with the left leg slightly bent at the knee and hip joints to ensure maximum stability on the operating table.
Surgical access technique
The approach is traditionally performed in the right temporal region.
- The surgeon makes a horseshoe-shaped incision of the skin and subcutaneous adipose tissue. The shape and line of this incision anatomically correspond to the line of attachment of the temporalis muscle. Note: in certain clinical situations, a vertical incision is permissible.
- The formed skin-aponeurotic flap is carefully dissected from the underlying tissues and reflected downward toward its base, which is located at the level of the zygomatic arch.
- Moving to the deep layers, the temporal aponeurosis and the interfascial adipose tissue are incised in a vertical direction.
- The temporalis muscle along with the adipose tissue is separated down to the bone.
Craniectomy and opening of the dura mater
After exposing the temporal bone, the periosteum is incised with a surgical scalpel. Then, using a raspatory, it is stripped over an area of about 6 cm².
Creation of the bone window: First, a burr hole is made, which is then progressively enlarged using special bone rongeurs. A critical topographic rule: the lower part of the created hole must be covered by the zygomatic arch. This is done for a specific purpose — in the postoperative period, the bulky mass of the temporalis muscle will serve as a natural barrier preventing the herniation (pathological protrusion) of the brain tissue into the bone defect.
Management of the dura mater: If the dura mater is severely tense, premedication must be performed before opening it — a lumbar puncture with the slow withdrawal of 10–30 mL of cerebrospinal fluid. This manipulation is critically important to prevent herniation syndrome — the entrapment of the brainstem into the foramen magnum during a sharp pressure drop. The dura mater itself is incised cruciately. If necessary, additional radial incisions are made. The final size of the opening in the membrane directly depends on the degree of intracranial hypertension: the higher the ICP, the wider the opening should be.
Danger zones and completion of the operation
When enlarging the bone window with rongeurs in an anteroinferior direction, the surgeon enters the danger zone. Here, there is a high risk of iatrogenic injury to the trunk of the middle meningeal artery (a. meningea media).
If injury to the artery does occur, the hemostasis algorithm depends on the location of the vessel ends:
- The peripheral end of the artery is securely ligated with a transfixion suture.
- The central end, which is most often located deep within the bone canal, is tightly sealed with sterile bone wax.
Wound closure: At the final stage of the surgery, layered closure of the soft tissues of the head is performed. The main feature of decompressive craniectomy is that the dura mater is not sutured. It remains open to ensure adequate decompression of the edematous brain tissue.
Briefly: answers to topical questions
What are the layered boundaries of the temporal region of the skull during a surgical approach?
The boundaries of the temporal region are defined by bony landmarks and muscle contours.
- Anterior boundary — zygomatic process of the frontal bone and frontal process of the zygomatic bone.
- Lower boundary — zygomatic arch (arcus zygomaticus).
- Upper and posterior boundaries — the contour of the upper edge of the temporalis muscle, defined by the temporal line (linea temporalis).
What anatomical structures are damaged when incising the temporal aponeurosis?
When incising the temporal aponeurosis, its superficial and deep layers are encountered, as well as the structures of the interfascial space:
- Superficial and deep layers of the temporal fascia (fascia temporalis) — the fascia splits into them 3–4 cm above the zygomatic arch.
- Interfascial adipose tissue — located between the layers of the fascia.
- Blood vessels — located in the interfascial space.
Which vessels and nerves supply and innervate the tissues of the temporal region?
The blood supply and innervation of the tissues of the temporal region are provided by superficial and deep neurovascular formations.
- Superficial temporal artery (a. temporalis superficialis) — divides into frontal and parietal branches; the middle temporal artery also originates from it.
- Deep temporal arteries (aa. temporales profundae) — branch off from the maxillary artery.
- Auriculotemporal nerve (n. auriculotemporalis) and in the posterior sections lesser occipital nerve (n. occipitalis minor) — provide sensory innervation to the skin.
- Branches of the facial nerve (rr. frontalis et zygomaticus) — innervate the muscles of facial expression.
- Deep temporal nerves (nn. temporales profundi) — innervate the temporalis muscle.
How does Cushing's decompressive craniectomy differ from osteoplastic craniotomy?
The main difference lies in the fate of the bone flap and the dura mater.
| Characteristic | Decompressive craniectomy | Osteoplastic craniotomy |
|---|---|---|
| Goal | Reduction of intracranial pressure | Surgical approach to the cranial cavity |
| Bone flap | The area of the temporal bone is resected (removed) | Preserved on a vascular pedicle and returned to its place |
| Dura mater | Incised cruciately and not sutured | Involves layered wound closure |
To avoid confusion on the exam regarding the closure stages, remember the rule: "The membrane breathes, the tissues close." We suture the soft tissues (skin, aponeurosis, muscle) in layers, while leaving the dura mater gaping for decompression.
Class and exam questions
Why should the lower part of the trepanation opening be covered by the zygomatic arch?
This is necessary so that the temporalis muscle, resting on the zygomatic arch, creates a solid muscular framework. This will prevent the prolapse (excessive herniation) of the edematous brain outward in the postoperative period.
For what purpose are 10–30 ml of CSF drained before incising a tense dura mater?
Cerebrospinal fluid removal via lumbar puncture smoothly reduces intracranial pressure. This prevents a fatal complication — a sharp herniation of the brainstem into the foramen magnum at the moment the membrane is opened.
How to stop bleeding in case of accidental injury to the middle meningeal artery (a. meningea media) within the bone canal?
The central end of the damaged artery, located in the bone canal, is sealed (plugged) with a special bone wax, and the peripheral end is ligated with a transfixion suture.
What else to study on this topic
- Topographic anatomy of the temporal region and its layers.
- Surgical instruments for trepanation (raspatories, bone rongeurs, burrs).
- Types of intracranial hemorrhages and hemostasis methods in neurosurgery.
- Mechanisms of brainstem herniation (dislocation syndromes) in increased ICP.
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