A craniotomy is a common neurosurgical procedure in which a bone flap is removed from the skull in order to access certain regions of the brain or overlying meninges. Among cranial procedures, which represent roughly a third of neurosurgery, craniotomies are performed in approximately half of the cases. Craniotomies may be performed in a number of locations (eg, pterional, suboccipital, frontal) to treat a wide variety of intracranial conditions (Table 26-1), including cerebrovascular lesions and brain tumors and for implantation of hardware (eg, cerebrospinal fluid shunts (CSF) or deep brain stimulators).

A variety of complications affect up to 1 in 4 patients undergoing a craniotomy¹, and these may be related to the craniotomy itself, specific to the condition being treated, or to hospitalization in general. Complications that may occur after most craniotomies (Table 26-2) include neurologic complications (eg, intracranial hemorrhage, seizures), medical complications (eg, blood pressure derangements, cardiac events), infection (eg, pneumonia, meningitis), and general surgical complications (eg, wound dehiscence). The range of postoperative complications depends on numerous factors, including location and features of operative site, patient clinical and demographic factors, and hospital factors (eg, duration of operation, length of hospitalization).¹

Although neurologic injury is a complication that must be mentioned to a patient before any brain surgery, it is avoidable in the vast majority of cases with a combination of careful surgical planning, preoperative testing, and specific intraoperative techniques to minimize risk. To start, a detailed preoperative neurologic examination is essential to discerning old and new deficits.

In tumor surgery, for example, numerous intraoperative techniques are utilized to minimize the chance of developing a new neurologic deficit while maximizing tumor resection. If a tumor is near the motor strip or language areas, the craniotomy can be performed awake with intraoperative language mapping and corticography. With language mapping, the patient undergoes extensive preoperative neuropsychiatric testing to serve as a baseline. Resting state MRI and diffusion tract imaging can also provide information to guide surgical resection while avoiding eloquent brain areas. Finally, stereotactic guidance is utilized in the operation during which the patient’s head is registered in the computer system, and multiple cameras show the surgeon where the surgical instruments are in relation to the eloquent brain areas and the tumor.

As another example, during a carotid endarterectomy, the patient often undergoes intraoperative monitoring with electroencephalography (EEG) and transcranial Doppler (TCD) to inform the surgeon of acute changes in cerebral perfusion during the procedure. At the time of cross-clamping the carotid, if the ipsilateral EEG decreases in amplitude or if the TCD demonstrates significantly decreased flow, the surgeon will place a temporary shunt to permit the continual flow of blood through the carotid bifurcation into the internal carotid artery while the surgeon removes the atherosclerotic plaque. During aneurysm surgery, for example, the surgeon might cool the patient or use EEG monitoring to be able to place a temporary arterial clip on the intracranial vessel proximal to the aneurysm so as to safely manipulate the aneurysm, dissect it away from surrounding structures, and place the aneurysm clip.

Cerebrovascular Events

Although significant hemorrhagic or ischemic stroke is generally uncommon after craniotomies, the associated mortality and morbidity rates are high. Clinically significant intracranial hemorrhage (ICH), which occasionally occurs away from the site of surgery, complicates 0.5% to 6.9% of craniotomies, and usually occurs within the first 24 to 48 hours postoperatively.^2,3 In addition to hematological risk factors such as medications (antiplatelet agents, anticoagulants) and low platelet count (< 100 000/μL), the nature of the surgery significantly affects risk. For example, the risk is consistently very low in deep brain stimulation (DBS) surgery, but far higher in patients undergoing treatment for vascularized tumors (eg, hemorrhage into residual tumor) or cerebrovascular lesions. Postoperative ischemic stroke with a significant, persistent neurologic deficit occurs in 2% of craniotomy cases overall. Ischemic stroke may result from thrombosis of a manipulated artery or vein, especially if a major venous sinus is disrupted by the craniotomy or from compromised cerebral perfusion. Venous hemorrhage must also be considered in any patient suffering delayed neurologic decline after a craniotomy. Most often, this syndrome presents with bilateral strokes in nonvascular territories or bilateral hemorrhages. This complication is more likely following resection of a brain tumor abutting the posterior two-thirds of the sagittal sinus.

Seizures

Seizures also tend to be an early complication after craniotomy and may result from any manipulation or disruption of the brain parenchyma. Although generalized tonic-clonic seizures are the most common type in the NeuroICU, some patients may present with neurologic deterioration and a decreased level of consciousness rather than convulsions, which may be missed without EEG, monitoring.⁴ With appropriate seizure prophylaxis, the incidence of seizures is approximately 3% to 8%.^5–7 Risk factors for postoperative seizures include a history of preoperative seizures, low serum levels of anticonvulsive agent, metabolic derangements, surgery for epilepsy, resection of supratentorial brain tumors, clipping of an aneurysm after subarachnoid hemorrhage (SAH), and traumatic brain injury.^7,8 Occasionally, after functional procedures, seizures may develop from an epileptic focus as a result of gliosis (scarring).

Cerebral Edema and ICH

Cerebral edema refers to an increase in brain water content, which may occur in association with SAH, ICH, tumors, trauma, seizures, and inflammatory diseases.¹⁰ Cerebral edema usually is a delayed complication in hemorrhagic strokes, peaking 48 to 72 hours after the ictus. Worsening cerebral edema can cause intracranial hypertension, which usually presents with headache, nausea, vomiting, papilledema, and often abducens (VI) palsies in the early stages of the disease process. If intracranial pressure (ICP) continues to increase, later signs include the Cushing reflex, which consists of hypertension, bradycardia, and irregular respiration, and potentially fatal herniation syndromes may occur. Cerebral edema is treated immediately by raising the head of bed and hyperventilating the patient. Medical treatments include mannitol, hypertonics, and then potentially, pentobarbitol coma and hypothermia. Surgical interventions include placement of an ICP probe for monitoring, placement of an external ventricular drain (EVD) for CSF control and ICP monitoring, and decompressive craniectomy. Common craniectomies include the hemicraniectomy, which is used to treat malignant stroke syndrome and subdural hematoma. It consists of removal of the unilateral frontal, temporal, and parietal bones from the floor of the middle fossa to the sagittal sinus. The bifrontal craniectomy (Kjellberg procedure) is commonly used to treat cerebral edema secondary to bifrontal contusions following trauma and consists of skull removal from the orbital rim to the coronal suture bilaterally.

Herniation

Herniation is the result of increased ICP. Postoperatively, a variety of herniation syndromes (eg, transtentorial, uncal, tonsillar) may be due to cerebral edema or to space-occupying lesions, especially large, postoperative ICH. Herniation usually presents with acute neurologic deterioration, which, depending on the type of herniation, may include decreased consciousness, a characteristic sequence of limb posturing, pupil dilation, and cardiopulmonary derangements.¹¹ A rare but fatal form of herniation can occur following resection of a large frontal meningioma in which the patient suffers severe edema and brain swelling even after resection of the large mass.

Hydrocephalus

Postoperative hydrocephalus is particularly common after posterior fossa surgeries, ranging from 4.6% to 30.0% of operations.^12,13 Although early signs of postoperative hydrocephalus may include headache, nausea, vomiting, and abducens nerve palsy, the most common presenting symptom is a decreased level of consciousness, which unfortunately is a relatively late finding.¹² Occasionally, hydrocephalus may present with a CSF leak.¹²

CSF Leaks

CSF leaks occur as a result of poor wound closure, such as incomplete water-tight dural closure, loose stitching of the galea, or postoperative hydrocephalus. In posterior fossa surgeries, the incidence is approximately 13%.¹² CSF leaks usually present in the immediate postoperative period, where the clear, watery CSF fluid may drain from the ear (CSF otorrhea), nose (CSF rhinorrhea), and/or throat via the Eustachian tube or the wound; in leaks from the incisional site, there is often a palpable collection.¹⁴ A palpable, subcutaneous collection of CSF is a pseudomeningocele. Prompt diagnosis and treatment are crucial, because CSF leaks confer a high risk of meningitis.^12,14 The first line of treatment is to increase the dose of steroids and observe. If the pseudomeningocele does not improve over time and/or appears to threaten the wound, reoperation is necessary.

Pneumocephalus

Pneumocephalus refers to the entry of air into the cranium through defects in the craniotomy site; most factors that cause CSF leaks may also result in pneumocephalus. Another cause of pneumocephalus is communication between the intracranial space and air cells in the bone associated with the pneumatized sinuses, such as the mastoid, frontal, ethmoidal, or sphenoidal air cells. If violation of a pneumotized sinus is suspected during surgery, the entrance is copiously waxed to prevent the flow of air or fluid. A small amount of air entry is a relatively unavoidable consequence of craniotomy, and fortunately most cases are not clinically significant. Patients with significant pneumocephalus may present with headaches, lethargy, seizures, nausea, and vomiting.¹⁵ The standard treatment is to keep the patient flat and administer 100% supplemental oxygen through a nonrebreather mask.¹⁵

Complications of Positioning and Pinning

Although practices of patient positioning and pinning for head fixation (eg, with the Mayfield head-holder) vary to some degree, there are several common complications that may occur to patients undergoing craniotomy. Complications from pinning may include malpositioning of pins through unintended structures, such as the superficial temporal artery, or overtightening of pins may result in skin necrosis. All contact points between the patient and operating table or associated straps must be well padded to prevent peripheral nerve injuries. In addition, head rotation, hyperflexion, hyperextension, or lateral flexion may compromise cerebral arterial and venous flow. The supine position, the most frequently used in neurosurgery, is generally very safe, although CSF drainage may be somewhat reduced compared with more upright positions.¹⁶ Lateral positioning carries a risk of stretch injuries to the upper extremity (eg, to the brachial plexus). Prone positions present a significant challenge to airway management, and venous return to the heart is decreased; in addition, patients are at risk for periorbital or conjunctival edema. Occasionally, a craniotomy may be performed when the patient is in the seated position (eg, for posterior fossa lesions), which places them at increased risk of air emboli.¹⁷ A cardiac Doppler is used to monitor the heart for the passage of air emboli and a central venous line can be used to aspirate air from the right atrium.

Shunt Complications

Ventricular shunts are primarily used to manage hydrocephalus, which may occur in a variety of neurologic conditions for which a craniotomy is performed. Among ventriculoperitoneal (VP) shunts, the most common type of shunt, failure rates are as high as 40% at 1 year; at least a quarter of patients require shunt revision surgery, and shunt infection occurs in 6.1% to 10.5% of cases.^18–20 The reason for shunt revision is most commonly mechanical obstruction (usually of the ventricular catheter or valve), followed by catheter malposition, infection, and overdrainage or subdural hematoma.¹⁹ Ventriculoatrial (VA) shunts, which are less commonly used, have higher rates of failure (49.7% vs 33.8% in VP shunts).¹⁹ The highest rate of shunt infection is within the first month after surgery, and this risk increases with the number of revisions performed.

The physiological stress of undergoing major surgery and general anesthesia, as well as the presence of preexisting medical comorbidities, increase the likelihood of acute cardiac and pulmonary events as well as delayed electrolyte, metabolic, and renal disturbances. Among patients undergoing craniotomy for a meningioma, a condition in which medical comorbidities largely do not play a role and thus confer minimal selection bias,²¹ the overall rate of serious, noninfectious medical complications has been cited at 6.8%. However, in patients with a history of chronic obstructive pulmonary disease (COPD), hypertension, carotid stenosis, stroke, coronary artery disease, cardiac arrhythmias, or cirrhosis, this risk is approximately 15% to 20%.²¹

Cardiovascular and Blood Pressure Lability

Fortunately, among craniotomy procedures the incidence of severe cardiac complications (myocardial infarction or cardiac arrest) is very low, at approximately 0.86%, and they tend to occur in patients with pre-existing coronary artery disease who are less likely to tolerate the physiological stress of surgery.²² However, subclinical, myocardial infarction-like changes may be noted during recovery in the NeuroICU, especially in patients with SAH.²² Blood pressure lability may be the result of primary cardiovascular processes, volume status, or may be due to neurologic causes. The incidence of postoperative hypertension is relatively high, ranging from 30% to 80% depending on definition of hypertension.²³ Sudden increases in blood pressure may be secondary to new-onset hemorrhagic or ischemic stroke or may represent a reflexive response to intracranial hypertension (the Cushing reflex), the presence of which carries a poor prognosis. Hypertension itself increases the risk of postoperative complications, including myocardial infarction, stroke, and ICH.^24,25 Hypotension is less common, affecting 2% to 5% of craniotomy cases, but may indicate an equally deleterious disease process. Hypotension may be the result of systemic causes (eg, cardiac arrhythmias, sepsis, pulmonary embolism), seizures, or adverse effects of drugs affecting autonomic blood pressure regulation. Notably, severe hypotension may result in cerebral ischemia, in particular in a “watershed” pattern.

Venous Thromboembolism

Venous thromboembolism (VTE), which includes pulmonary embolism (PE) and deep vein thrombosis (DVT), is considered a largely preventable cause of mortality and morbidity among hospitalized patients. Among neurosurgery patients undergoing cranial procedures, the rates of DVT and PE are 2.6% and 1.4%, respectively.²⁶ Risk factors include immobility (eg, hemiplegia due to stroke), ventilator dependency, prolonged bed rest, increased length of stay, severe infection, and presence of systemic malignancy.^26,27 VTE prophylaxis with enoxaparin (Lovenox) or subcutaneous heparin injections is standard on postoperative day 2 in most centers for patients undergoing complex spine and intracranial procedures.

Pulmonary

Noninfectious, nonthromboembolic pulmonary complications include exacerbation of obstructive diseases (eg, COPD), atelectasis, and bronchospasm.²⁸ Rarely, neurogenic pulmonary edema may occur after hemorrhage, seizure, or trauma. Aspiration pneumonia and atelectasis are common causes of postoperative fever. To minimize the chance of aspiration pneumonia, patients are kept NPO (nil per os = nothing by mouth) for at least 6 hours before surgery. To decrease the chance of postoperative atelectasis, patients are encouraged to use incentive spirometry at least 6 times per hour while in the hospital after the operation.

Gastrointestinal

Nausea and vomiting are common complications after neurosurgery, affecting 47% of patients after craniotomy.²⁹ Not only may emesis result in aspiration—in a patient population that often has impairment in consciousness, but vomiting and retching may result in swelling or hemorrhage at the surgical site.²⁹ Risk factors are primarily related to the pharmacological effect of anesthetic drugs (eg, female gender, history of postoperative nausea or vomiting, duration of surgery, use of postoperative opioids, nonsmoking status). Although the administration of intraoperative corticosteroids can decrease the incidence of postoperative nausea and vomiting, they also increase the risk of ulceration and gastrointestinal (GI) bleeding, so a proton pump inhibitor must also be administered.^29,30 Of note, however, nausea and vomiting may also be an ominous sign of increasing ICP, which can be life threatening. Other GI complications that may occur more rarely are those related to prolonged bed rest and enteral or intravenous (IV) feeding.

Endocrine and Metabolic Complications

Endocrine, electrolyte, and metabolic complications may occur after craniotomy as a result of intracranial disease processes which may affect hypothalamic function, or disturbances that may affect NeuroICU patients (eg, as a result of fluid management, use of hyperosmolar agents, feeding). In addition, the frequent use of hyperosmolar agents (eg, mannitol) may precipitate acute renal failure.³¹ Patients with diabetes, in particular, are at risk of glycemic derangement. Serum sodium abnormalities are also relatively common after craniotomies and may be related to central diabetes insipidus, SIADH (syndrome of inappropriate antidiuretic hormone secretion), or cerebral salt wasting syndrome. Hyponatremia is common, affecting 30%-50% of patients.³² Under- or overtreated sodium derangements may result in a number of neurologic adverse events including seizures, cerebral edema, and central pontine myelinolysis (CPM).³² To avoid CPM, do not permit a patient’s serum sodium concentration to increase at a rate faster than 0.5 mEq/h.

Pain

Postoperative pain is an underrecognized problem in patients who undergo craniotomy. As many as 87% of patients experience pain after craniotomy, of whom 44% report moderate and 10% report severe pain despite treatment with potent analgesics.³³ In addition to the distressing subjective experience, pain increases sympathetic tone, which, notably, may induce hypertension and increase the risk of ICH.^25,33 Risk factors for postcraniotomy pain include female gender, infratentorial operation, splitting of extracranial muscles (eg, temporalis, posterior cervical muscles), and older age. Notably, an intraoperative protective factor for postcraniotomy pain is administration of corticosteroids.³³

In neurosurgery as well as in many other specialties, nosocomial infections have been a focus of quality improvement initiatives and recent healthcare reform.^34–36 Infections tend to be delayed complications, typically occurring after postoperative day 3 or 4. General risk factors for infectious complications include increased length of stay, longer operation duration, emergency procedures, prolonged bed rest (eg, due to significant neurologic deficits), early reoperation, high American Society of Anesthesiologists score, older age, admission to the intensive care unit (ICU), and immunocompromised status (eg, chemotherapy, prolonged use of corticosteroids, uncontrolled diabetes).^37–41

Meningitis and Surgical-Site Infections

Unlike most other infections listed in Table 26-2, postoperative meningitis and surgical-site infections (SSIs) may in large be directly attributed to technical details of the neurosurgical procedure itself. The overall incidence of postcraniotomy meningitis (which may be considered a deep or organ-space SSI) is 1% to 8%⁴², and the rate of SSIs is 1% to 5%.^43–45 Risk factors specific to meningitis and SSIs include, notably, wound dehiscence, presence of foreign material at the surgical site, postoperative leakage of CSF, and use of a dural substitute.^45,46 Unlike community-acquired meningitis, meningitis associated with neurosurgical procedures is due to Staphylococcus aureus in approximately a third of cases. In addition, in nosocomial meningitis, nuchal rigidity is far less common, being present in less than half of cases^.. It also tends to present with more nonspecific symptoms, primarily fever and altered mental status. Although perioperative prophylaxis with cefazolin has decreased the number of cases due to S aureus, it does not cover gram negatives, which may be responsible for up to a quarter of cases at certain institutions.⁴⁵

Cerebral Abscess (Subdural Empyema)

In addition to those that occur by hematogenous spread (eg, in patients with endocarditis and pulmonary vascular malformations), cerebral abscesses may occur after cranial neurosurgical procedures or head trauma, especially in cases where an air sinus is violated.⁴⁷ The presentation is often nonspecific and insidious; most have headache, although fever is frequently absent, blood cultures are often negative, and neurologic signs depend on the site of the abscess. In addition, a quarter of patients present with seizures.⁴⁷

Pneumonia

With prophylactic use of antibiotics, the incidence of pneumonia is as low as 2.5%, although for neurosurgical patients in the NeuroICU this figure is greater, at approximately 10% to 20%.^48,49 The strongest risk factor for nosocomial pneumonia is, by far, mechanical ventilation (ie, ventilator-associated pneumonia); others include unplanned reintubation and presence of chronic lung diseases (eg, COPD).⁵⁰ Pneumonia disproportionally affects neurosurgical patients who have depressed consciousness, as this is an indication for endotracheal intubation in the NeuroICU. For example, in patients with SAH, the incidence of pneumonia is as high as 20% to 30%.^51,52 Unlike community-acquired pneumonia, nosocomial pneumonia is commonly due to more treatment-resistant organisms including S. aureus, Pseudomonas aeruginosa, Acinetobacter, and Klebsiella.⁵³

Urinary Tract Infections

Overall, urinary tract infections (UTIs) are the most common healthcare-associated infection in the United States.⁵⁴ In patients undergoing a craniotomy, the overall risk of a UTI is approximately 3% to 7%.⁵⁵ Risk factors specific to a UTI include urethral catheter use (responsible for the majority of nosocomial UTIs), duration of catheter use, female gender, and bacterial colonization of the drainage bag.⁵⁶ Nosocomial UTIs are a significant issue in the NeuroICU in particular, where most patients are catheterized.⁵⁷ The most common cause is Gram-negative organisms, most often Escherichia coli and less commonly Klebsiella.⁵⁸