Craniotomy Periprocedural Care

Informed consent is the process of explaining the risks, benefits, and alternatives of the planned craniotomy to the patient. This is done by the neurosurgeon and can be supplemented with teaching materials at the neurosurgeon's discretion. Patients nowadays have more access to information through multiple online resources, which can help to prepare the patient for the planned procedure. The informed consent is typically conducted in the neurosurgeon's office prior to the planned procedure, or in the hospital if the patient has developed an acute issue. There are occasions where the patient is incapacitated by the brain pathology so that consent must be obtained through a designated health care proxy, spouse or sibling, and rarely in emergency cases, by means of two attending physicians, one of whom is the operating neurosurgeon.

Prior to undergoing craniotomy, all patients will have undergone some type of brain imaging.

Computed tomography (CT) of the head is the most widely used and accessible form of brain imaging, and along with CT angiography (abbreviated as CTA, useful for vascular pathology such as aneurysms and AVMs), they continue to play a major role in operative planning.

Magnetic resonance imaging (MRI) has largely replaced CT scanning in the delineation of brain tumors while continuing to expand its role in stereotactic neurosurgery (image guidance). Its application remains vast and has become standard in nearly all planned craniotomy operations.

In certain circumstances, diagnostic cerebral angiography may be the primary mode of imaging, although a patient nearly always undergoes angiography based on a finding initially identified on CT or MRI.

In addition to brain imaging, a patient’s preoperative assessment may include a recent set of basic blood tests, electrocardiogram (ECG), and chest radiography, depending on the patient’s medical history and recommendations of the treating physician. These studies are generally grouped into the pre-admission testing category done for nearly any scheduled craniotomy.

A few fundamental tools are required to accomplish a standard craniotomy or craniectomy. The setting for a craniotomy is a controlled, sterile environment in a designated operating room. The basic objective is to remove the bone flap as safely as possible, taking great pains to minimize blood loss, to reduce the potential for infection, and to limit damage to the underlying brain. The essential instruments for performing a craniotomy are as follows:

• Skin knife (scalpel): No. 10 blade is typically used to make the skin incision

• Suction tips and tubing (eg, Frazier tip): For clearing blood from the surgical field to maintain visibility; microsuction and variable suction devices are typically utilized when the brain itself is entered

• Raney clips and tissue retractors (Adson cerebellar, Weitlaner, Jansen): The clips are placed on the scalp edges to stop bleeding, while the retractors serve to keep the incision open

• Leyla bar and fish hooks: An optional setup that allows retraction of scalp and muscle for the duration of the operation, most often used for a pterional craniotomy

• Monopolar electrosurgical unit (eg, Valleylab, Covidien): Often referred to as a Bovie, this instrument offers two functions (cut and coagulation) for dissection through subcutaneous tissue, fascia, and muscle while preserving hemostasis

• Bipolar electrosurgical unit (eg, Codman, Malis): Provides focused electrocautery of blood vessels as a means of stopping bleeding; can also be used to safely coagulate dura and to dissect both normal and abnormal brain tissue

• Periosteal elevator: Used to lift the periosteum off the skull prior to drilling

• High-speed air drill (eg, Midas Rex, Zimmer): Accommodates various drill bits, including burrs and perforators (used to penetrate the skull and form a burr hole), as well as the craniotome with foot plate (used to carve out a bone flap from the initial burr hole)

• Flap elevator and Penfield dissector no. 3: Both used to lift the bone flap after the craniotome has drilled out a window of bone

• Craniotomy miniplate and screw set (eg, Lorenz, Codman): Titanium low-profile plating system used for replacing the bone flap after the intracranial surgery is complete ^[7]

Given the importance of minimizing blood loss during a craniotomy and the subsequent intracranial surgery, medications that are considered "blood thinners" should be discontinued prior to surgery. These include nonsteroidal anti-inflammatory medications (NSAIDs, eg, aspirin and ibuprofen), antiplatelet agents (eg, clopidogrel [Plavix]), and anticoagulant medications (eg, warfarin [Coumadin]). With the proliferation of newer age blood-thinning agents (eg pradaxa, eliquis), some of which may be unfamiliar to the treating neurosurgeon, more attention must be paid to the patients' mediation list. Patients should also be counseled to stop smoking and drinking alcohol prior to a craniotomy.

The treating neurosurgeon may also initiate preoperative steroid therapy (eg, with dexamethasone [decadron]) to reduce cerebral edema due to an intracranial mass lesion, as well as antiepileptic therapy (phenytoin [Dilantin] or levetiracetam [Keppra]) if there is a significant concern for potential seizures. If the craniotomy is part of an operation that will involve manipulation of brain tissue, an additional steroid dose is typically given in the operating room prior to incision (10-20 mg IV dexamethasone). Likewise, a loading dose of an antiepileptic drug is given for the same circumstance (eg, 1 gram of fosphenytoin or phenytoin [15-18 mg/kg body weight], 1000-1500 mg of levetiracetam).

It has now become standard practice for an intravenous antibiotic to be administered in the operating room approximately 30 minutes prior to the surgery (eg, cefazolin [Ancef], vancomycin, clindamycin) with the goal of reducing the likelihood of wound infection from neighboring bacterial skin flora (most commonly Staphylococcus aureus). For some craniotomies, typically those involving a large mass lesion with significant underlying edema and brain shift, a diuretic (mannitol) is administered during skin incision for additional brain relaxation at a dose of 0.5-1 g/kg body weight. ^[3]

Two broad categories of anesthesia are used for a craniotomy: local and general. Most craniotomies involve both methods of anesthesia; local anesthetic is injected into the incision site for superifical hemostasis and postoperative pain control, while general endotracheal anesthesia (GETA) is administered for the duration of the operation.

In certain circumstances, an awake craniotomy is performed so that the patient can be awoken and interact during the critical portions of the case, and this requires greater emphasis on local anesthesia and intravenous administration of sedatives during the operation. ^{[8, 9, 10]} An awake craniotomy involves a combination of local and general anesthesia via intravenous agents, but does not involve insertion of an endotracheal (ET) tube. This type of anesthesia is commonly referred to as monitored anesthesia care (MAC), which is marked by the absence of an ET tube and the lack of inhalational agents. MAC is used for awake craniotomies and smaller, shorter operations such as the drilling of burr holes. The advent of more advanced anesthetic agents (eg, precedex and remifentanil) and higher-definiton navigational software (including functional MRI) for eloquent region mass lesions have expanded the use of MAC and awake craniotomy approaches. In particular, this is being done with increasing frequency in the case of tumors that were once considered unresectable.

The local anesthetic agent used for craniotomies is typically characterized by a rapid onset of action and intermediate duration of action. Lidocaine (0.5%-2%) is the most commonly used medication. Additionally, the local anesthetic is mixed with a dilution of epinephrine (1:100,000-1:400,000), which confers local hemostatic control via vasoconstriction. This vasoconstrictive effect also counteracts the vasodilatory effect of the anesthetic agent, thus prolonging its duration of action at the injection site.

GETA for craniotomies, commonly referred to as neuroanesthesia, involves two categories of medications: inhalational agents and intravenous agents. There are a number of factors of special concern to the neuroanesthesiologist before and during a craniotomy. These parameters and a brief description of their importance to the operation are as follows:

• Blood pressure: May have to be raised or lowered depending on the operation; its control is paramount to the anesthesiologist, as it affects cerebral perfusion pressure (CPP) and bleeding; monitored continuously via arterial line

• Arterial CO₂ tension (PaCO₂): As a potent vasodilator, CO₂ must be closely monitored and can be manipulated by the anesthesiologist, as hyperventilation reduces PaCO₂ and leads to vasoconstriction and less cerebral blood flow (CBF); the goal during and immediately after a craniotomy is an end-tidal CO₂ (ETCO₂) of 25-30 mm Hg, which correlates to a PaCO₂ of 30-35 mm Hg

• Hematocrit: Monitoring blood loss intraoperatively and transfusing blood as necessary is a critical aspect of maintaining the patient's circulatory status during the operation

• Temperature: Mild hypothermia has demonstrated protection against cerebral ischemia and is used in certain neurosurgical procedures ^[11]

Inhalational drugs in use today tend to be halogenated agents that have in common the properties of suppressing EEG activity and offering some element of cerebral protection. Included in this category are isoflurane, desflurane, and sevoflurane. Intravenous agents of choice include propofol, which is often used because of its short half-life, for induction of general anesthesia, as well as a continuous infusion for total intravenous anesthesia (TIVA). Less often used in this latter category are barbiturates, etomidate, and ketamine. Narcotics are also used as intravenous agents during general anesthesia for a craniotomy; remifentanil and fentanyl are more commonly administered, particularly in awake craniotomies as noted above. ^[11]

In many ways, the positioning of the patient is the most critical step in performing an effective operation. It begins with the choice of how to situate the patient’s head, or head fixation.

Head position

There are two basic ways of positioning the head: unfixed and fixed.

The unfixed approach is typically used when rapid access is necessary or stabilization of the head is not essential. This involves placing the head on a head-holding apparatus, often a padded cerebellar headrest (also called a horseshoe) or a simple "doughnut" (a circular foam with the middle portion cut out). In children younger than 3 years, pins are not recommended owing to increased risk of depressed skull fractures, so a cerebellar head rest is used. In children aged 3-10 years, special pediatric pins are recommended.

Head fixation is achieved with 3 skull pins that are situated in a head clamp (eg, Mayfield head-holder). The location of the craniotomy dictates where the pins are placed in the patient’s skull. Some basic principles include placement of pins above the orbits and pinna; avoidance of thin areas of the skull, such as the temporal squamosa and the frontal sinus; placement of the single pin anteriorly when the patient is positioned supine; and placement of the single pin on the same side of the craniotomy when the patient is positioned prone for a posterior fossa approach. ^[11]

When the desired pin positioning is achieved, the clamp is squeezed together, thereby seating the pins in the skull. The knob that houses the tension spring is screwed tightly until 60 pounds of pressure is registered. In pediatric patients, 30-40 pounds is the recommended limit. The clamp is then locked into the Mayfield adaptor, which is a series of joints extending from the head of the operating table. Care should be taken to avoid hyperflexion of the neck, which could lead to obstruction of the ventilated airway, and to avoid compression of the neck or jugular venous outflow, which could increase intraoperative bleeding. Other vulnerable areas include the ulnar nerves and the axilla, both of which require careful padding, especially in the lateral position.

Body position

Depending on the location of the intracranial lesion, there are various methods of positioning the patient on the operating table in order to maximize visualization and to improve ease of access to the target. There are 4 fundamental positions for a craniotomy: supine, prone, lateral, and sitting (see image below).

Below are five images showing how the patient's head is pinned in the Mayfield skull clamp and how the body is positioned. A) Supine with head neutral position, head pinned for a unilateral or bilateral frontal craniotomy; B) supine with head turned position, head pinned for a pterional or frontotemporal craniotomy; C) lateral position, head pinned for a suboccipital craniotomy; D) lateral position, head pinned for a more midline suboccipital craniotomy; E) semi-sitting position, head pinned for midline suboccipital craniotomy (image borrowed from Sekhar, Atlas of Neurosurgical Techniques: Brain)

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The following is a list describing these positions in greater detail, including a variation on the sitting position (semi-sitting) ^[12] :

• Supine position: The most common position; can involve the head in the neutral position or turned; allows access to the frontal, parietal, and temporal lobes; associated with craniotomies in all of these regions, as well as with the pterional craniotomy for Circle of Willis aneurysms; also used for transsphenoidal approaches to the pituitary region; can also be used for certain lesions of the posterior fossa such as cerebellopontine angle (CPA) masses, but this approach requires a significant head turn (nearly horizontal) and the aid of a shoulder roll

• Prone position: More narrow application; head is pinned in the neutral position; associated with occipital craniotomy and suboccipital craniotomy/craniectomy to access the posterior fossa

• Lateral position: Associated with suboccipital craniotomies for access to posterior fossa lesions, including retrosigmoid, far lateral and extreme far lateral approaches; can also be used for posteriorly situated lesions of the parietal lobe and lesions of the occipital lobe; modifications include the "park bench" position, a more exaggerated head turn that is used in certain approaches (eg, occipital trans-tentorial); another use is for deep-seated lesions, often in the ventricular system of the brain, where an interhemispheric approach is utilized; this approach develops a corridor between one frontal lobe and the falx cerebri, a large dural fold in the midline separating the frontal and parietal lobes of the brain

• Sitting position: Rarely used; used for access to the posterior fossa and pineal region; associated with a higher risk of venous air embolism, which is a potentially fatal complication

• Semi-sitting position: Associated with surgeries involving the pineal region, namely the supracerebellar infratentorial approach; can also include approaches to the posterior parietal region and occipital lobes; less risk of air embolism than a pure sitting position, but still higher risk than that of the recumbent positions

Operating room layout

Depending on the craniotomy, the patient’s physical positioning in the operating room varies. The key elements of the operating room include the patient on the operating room table, anesthesiology team, operating neurosurgeon and assistant, scrub tech, and intraoperative microscope. Other equipment fits into the room based on where these elements are situated (see image below).

Operating room setup for a right-sided frontotemporal craniotomy. Note the location of the patient, anesthesiologist, operating neurosurgeon, and scrub tech. (image borrowed from Sekhar, Atlas of Neurosurgical Techniques: Brain)

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Immediate postcraniotomy care

For nearly all types of craniotomy, the patient is observed for at least the first 24 hours in a neurological intensive care unit (NICU) or general surgical ICU. Basic laboratory tests are sent (complete blood cell count and basic metabolic panel). Neurological examinations are performed by the nursing staff every 1-2 hours, and any changes in neurologic status (eg, confusion, lethargy, aphasia, cranial nerve deficit, weakness, numbness) are immediately conveyed to the neurosurgical team.

In addition, the patient’s systolic blood pressure is kept between 90-140 mm Hg, since pressures above this range place the patient at risk for hemorrhage into the operative site, while pressures too low may compromise cerebral perfusion pressure and lead to possible infarcts. If necessary, an intravenous antihypertensive medication is administered (eg, intravenous nicardipine).

Antibiotics are continued for a total of 24 hours following the craniotomy. Dexamethasone is tapered depending on the surgery; a straightforward supratentorial craniotomy requires a shorter taper, over one week, while operations for malignant mass lesions (gliomas, metastases) and posterior fossa craniotomies receive a longer taper, over two weeks. Patients with malignant lesions are typically tapered down to and then maintained on a low dose of decadron that is subsequently managed by the treating radiation oncologist, neuro-oncologist, or general oncologist.

Antiepileptics are administered postoperatively at the discretion of the neurosurgeon; if the use of these drugs extends beyond a month, they are often managed in consultation with a neurologist.

Long-term monitoring

After the acute postoperative phase (24-48 hours of observation in an ICU setting), the patient is transferred to a hospital floor bed, where the recovery continues. For most craniotomies, on the first postoperative day, the patient’s blood pressure parameters are liberalized, Intraoperative monitoring devices are removed (arterial line, Foley bladder catheter), and the patient is encouraged to ambulate.

From the first postoperative day onward, functional needs are assessed by an assortment of therapists, if necessary (eg, physical therapy, occupational therapy, speech therapy), and plans for further care are implemented, such as an inpatient rehabilitation stay or outpatient physical therapy.

All dressings are removed on the second postoperative day, and the staples or sutures used to close the most superficial skin layer can be removed 5-10 days following surgery. Absorable sutures are being more commonly utilized due to the use of more minimally invasive incisions and approaches.

If the recovery proceeds without complication, patients can be discharged as soon as the first postoperative day, though more commonly on the second or third postoperative day. Hospitalizations can exceed this duration depending on the specifics of the surgery.

Routine postoperative follow-up includes an office visit to the treating neurosurgeon within 1-2 weeks after hospital discharge. For benign lesions (eg, meningiomas, pituitary adenomas) the neurosurgeon typically conducts the long-term followup with surveillance MRIs. For malignant lesions, a neuro-oncologist in the case of primary brain neoplasms (eg, glioblastoma) and oncologist in the case of metastatic tumors conduct the long-term followup, also with surveillance MRIs along with adjuvant treatment as well.

Patient education

Upon discharge, the patient and family are given specific instructions. If the patient notes clear leakage from the craniotomy incision, which could indicate CSF egress, an immediate call to the neurosurgeon is made. Bleeding from the incision site for the first few days following surgery is common and not concerning. If the wound itself is noted to be tender, red, or not healing well or the patient develops fevers and chills, the patient should contact the neurosurgeon. If the patient feels nauseous, vomits, notices visual changes (blurriness, field cuts), experiences increasing headaches, has word-finding difficulties, experiences cognitive slowing, has newly onset weakness and/or numbness, or is noted to be lethargic, confused, or difficult to arouse by family, an urgent call should be placed to the neurosurgeon.

In terms of wound care, the patient is allowed to shower on the third postoperative day but typically discouraged from a bath until 1–2 weeks later. Hair products other than baby shampoo are also discouraged for at least 2 weeks. Also, the patient is cautioned against picking and manipulating the incision. Most patients who undergo craniotomy are considered fit to return to most occupations 2–6 weeks following the operation.

Patients may also be cautioned against flying for 1–4 weeks given the possibility of exacerbating air pockets (pneumocephalus) that are introduced into the intracranial space during the craniotomy. Changes in cabin pressure may induce severe headaches.