Surgical Planning

Preoperative Evaluation

The first task of a surgeon before any procedure is a thorough and comprehensive evaluation of the patient. Preoperative patient assessment regularly consists of a detailed and focused history, physical examination, and review of pertinent laboratory results and imaging studies ( Fig. 21.1 ). Disciplined, repetitive practice in these tasks allow for a comprehensive, detailed, and repeatable preoperative course that minimizes error. Checklists often prove useful for this comprehensive coverage.

A patient’s history must begin with a clear definition of the presenting complaint. Subsequent delineation of temporal course and of onset of symptoms clarifies the degree of a suspected condition. In addition to establishment of pertinent positives, pertinent negatives should always be documented. This is essential in providing a record of preoperative deficits to compare with those encountered postoperatively. The side of hand dominance is an important feature to assess and document. Adherence to basic medical history taking is complete with review of medical and surgical history, medications, allergies, and familial and social history, including use of tobacco, ethanol, or illicit drugs. A general review of systems should also be included.

The physical examination includes a thorough neurological evaluation as well as a general physical assessment. The complete neurological examination should include evaluation of mental status, speech function and understanding, cranial nerve function (including that of the first cranial nerve), motor and sensory function, and reflexes, as well as cerebellar/gait testing. Of note, the sensory examination should include evaluation of proprioception and pinprick responses. Formal visual field and acuity examination may be required if there is concern for disease anywhere along the visual tracts, from the eye itself to the occipital lobe. Rectal examination for tone, volition, sensation, and the bulbocavernosus reflex is often required in evaluating spinal disease. Specific evaluation for surgical scars in the chest or abdomen may be valuable in the planning of a procedure that extends beyond the brain or spine, such as placement of a ventriculoperitoneal shunt.

Computer documentation provides the surgeon with a useful tool for systemic and comprehensive evaluation of the history and physical examination findings. However, the surgeon must be deliberate, being cognizant of the potential for error when glossing over standard templates. Finally, many neurosurgical patients have significant comorbid conditions that necessitate preoperative evaluation. The goals of surgery should always be considered as they relate to the patient’s overall medical status and personal preferences.

Routine laboratory values, including a metabolic panel and blood cell count, are indicated before any nonemergency surgical procedure and should be obtained to screen for a number of underlying acute or chronic pathologic conditions that may pose a risk to a patient undergoing general anesthesia and surgery. The metabolic panel may suggest variations in sodium and potassium levels often noted in the neurosurgical patient population, as well as baseline renal function. Underlying anemia noted in the blood cell count must be investigated and corrected accordingly. Any suggestions of infection, such as an elevated white blood cell count, positive cultures, erythrocyte sedimentation rate (ESR), or C-reactive protein level, should be investigated and treated, especially in elective cases or if hardware implantation is planned. Before definitive surgery, particular attention should be focused on platelet count, prothrombin time (international normalized ratio), partial thromboplastin time, and bleeding time (if necessary). Any suggestions of bleeding diathesis or coagulopathy should be further investigated and corrected. Many patients currently take anticoagulant or antiplatelet agents for a number of underlying medical comorbid conditions. Discontinuation or reversal of these agents (or perhaps initiation of these agents in selected endovascular cases) should be addressed at least 1 week before surgery. Blood typing and screening, or crossmatching for packed red blood cells and blood products should be requested from the blood bank and verified in advance. A qualitative β-human chorionic gonadotropin level should be measured for every woman of childbearing age before surgery.

Sellar disease often necessitates special preoperative consideration. Patients should undergo serum testing of a full or selective endocrine panel to evaluate any pituitary axis deficiencies. The thyroid and cortisol axes are uniquely critical, and abnormalities must be identified and corrected before any surgical procedure is performed. Ruling out nonsurgical lesions, such as prolactinomas, also necessitates judicious review of preoperative laboratory work.

Preexisting cardiac disease is common in the neurosurgical patient population. Preoperatively, a detailed cardiovascular history should be documented to assess exercise tolerance and to screen for angina or congestive heart failure. Common symptoms of heart disease are shortness of breath, chest pain, palpitations, and fatigue. Clearance by a cardiologist may be required if a patient has certain risk factors or symptoms. A 12-lead ECG and plain chest radiographs are obtained in the majority of adult patients before elective surgery. An ECG helps detect preoperative arrhythmias, conduction defects, chamber enlargement, and myocardial ischemia. It is also helpful as a baseline for comparison with subsequent changes. The plain chest radiograph is also helpful for evaluating pulmonary infiltrates, pulmonary vessel distention, or cardiac enlargement to suggest some form of cardiac disease. If further cardiac workup is indicated, an exercise treadmill test, echocardiography, nuclear medicine study, or coronary angiography may be performed to further assess the degree of cardiac risk and the need to optimize such risk before surgery. Hypertensive patients require adequate blood pressure control before elective surgery because there is a linear correlation between preoperative blood pressure and postoperative myocardial ischemia. In general, any existing cardiac risk factor must be addressed before a patient undergoes an elective neurosurgical procedure. The degree of cardiac risk, if present, should be accounted for and weighed against the urgency of the neurosurgical procedure. Any perioperative measures that may improve cardiac monitoring or function should be planned in conjunction with the anesthesia team, including normalization of electrolyte imbalances, optimization of fluid status, perioperative cardiac medications, and invasive cardiac monitoring. In the setting of baseline anemia or anticipated blood loss, especially in the setting of invasive high-risk spine surgery, large-bore intravenous access or central venous access is critical to the timely delivery of blood products and the prevention of hypovolemic intraoperative insult.

Baseline pulmonary disease is also common in the general neurosurgical population. Symptoms of pulmonary conditions include dyspnea, cough, sputum production, wheezing, and hemoptysis. Prior conditions such as recent respiratory infections, chronic obstructive pulmonary disease (COPD), and asthma must be elicited during history taking. Comorbid conditions such as asthma and COPD may hinder anesthesia during a neurosurgical procedure and must be addressed and optimized. Historical details, including a smoking history, merit special attention by the physician. Baseline oxygen saturations on routine vital signs may be a quick way to delineate pulmonary disease, inasmuch as room-air saturations below 93% are suggestive of at least mild respiratory failure. A preoperative plain chest radiograph helps show any preexisting infiltrates, atelectasis, masses, abnormal pulmonary vessels, or pneumothoraces. Further testing can be done with pulmonary function tests or a dedicated chest CT scan to rule out underlying pulmonary conditions. Perioperative medications, including steroids and beta agonists, may be indicated for patients with pulmonary disease and should be discussed with the anesthesia staff. For patients with significantly limiting pulmonary conditions, elective surgery should be postponed until pulmonary function has been maximized to reduce postoperative pulmonary morbidity. Severe ventilatory compromises may limit prone positioning for posterior fossa or spine surgery, and coincident structural lesions such as lung masses may dictate the laterality of certain neurosurgical approaches.

Some neurosurgical patients present with malnutrition or failure to thrive as a result of their disease process. Many conditions prevalent in the neurosurgical patient population render patients unable to consume a normal amount of calories to sustain normal metabolism. Because of mental status changes, weakness, paralysis, or any number of airway or cranial nerve issues, some patients rely on alternative methods of nutritional intake. These may include nasogastric tubes, percutaneous gastric tubes, or parenteral forms of intake for nutritional supplementation or full delivery. Before any neurosurgical case, a patient’s nutritional status should be considered and optimized. Serum prealbumin and albumin levels can be monitored to assess and follow a patient’s nutritional status. A clinical nutritionist can be invaluable in optimizing a patient’s nutritional status before a major surgery through calculations of standard and postoperative nutritional requirements. Patients who have undergone previous surgery or radiation therapy and those taking long-term steroids may require additional caloric requirements to achieve adequate wound healing. Diabetes mellitus, especially in the setting of poor glycemic control, may further compromise wound healing and should be addressed during the nutritional evaluation. Screening hemoglobin A _1c levels may help detect this clinical scenario.

Once the evaluation of a patient’s neurological and systemic disease has been thoroughly completed and a surgical plan outlined, a frank discussion with the patient and any other family members involved in the patient’s care should take place. The goals of surgery and any possible barriers to these goals should be clearly and honestly delineated. For nonemergency cases, the risks and benefits of the recommended procedure and the alternatives to the procedure should be reviewed and any additional questions answered by the surgeon. This discussion should also include a description of any permanent hardware implants that may be used, as well as the possibility of blood transfusions in high-risk cases. Time and patience are of utmost importance during this process to ensure that the patient fully understands all aspects of the surgery. An informed consent document should then be signed by the surgeon, patient, and any witnesses present for the conversation. Additional consent for any research protocols or tissue specimen banking should also be thoroughly discussed and performed.

Neuroimaging and Other Technologies

Before the initiation or formulation of any surgical procedure, the correct battery of neuroimaging studies should be obtained and carefully reviewed by the surgeon and radiologist. Consultation with a neuroradiologist may be beneficial in selected cases when a particular diagnosis is in question, to postprocess and interpret advanced neuroimaging studies, and to confirm whether nearby anatomic structures are at risk. Preoperative images frequently include plain radiographs, CT imaging, MRI, catheter angiography, and a variety of additional modalities. The surgeon should ensure that the correct sequences have been performed, have been reviewed, and are available during the procedure. The neuroimaging studies must be available in the operating room during the actual procedure because intraoperative anatomy must often be correlated with preoperative films. In addition to static images, dynamic studies of the spine such as flexion/extension views may provide insight into corresponding conditions. Although CT scanning and magnetic resonance angiography allow for a static anatomic evaluation of vasculature, catheter angiography may be helpful in defining diseases that have a time component of early or late filling. Certain pathologic entities such as arteriovenous malformations have abnormalities in flow; thus the time component must be considered in the preoperative evaluation.

Recent advents in technology, whether in imaging, virtual reality, or artificial intelligence (AI), have permitted the surgeon to obtain more knowledge than previously possible when planning for an operation. For example, tractography permits visualization of adjacent tissue to demonstrate the relationship between a tumor and its surroundings. Three-dimensional printing can be used to create tangible replicas for surgeons to better understand how best to approach a lesion. Virtual reality programs are now optimized to simulate real-time surgery with realistic anatomic structures and approaches to pathologies that can be integrated into the model. These tools have been developed and continue to be optimized to better prepare the surgeon for a case and should be utilized whenever possible.

Robotics are utilized less frequently in neurosurgery but are utilized more readily in other specialties such as urology and general surgery. The robots that currently exist for neurosurgery are still dependent on the surgeon for the intervention, but they guide the surgeon’s hand to allow for precision in placement. For example, in the United States, the US Food and Drug Administration (FDA) has approved the use of robots that were developed for both cranial and spinal applications. For example, a robot is frequently used to assist the surgeon when performing stereotactic procedures so the trajectory is controlled and the margin of error is as small as possible. Similarly, the placement of spinal pedicle screws, rods, and constructs can be done with machine assistance for three-dimensional navigation and real-time trajectory selection. These devices further protect the surgeon from error as they are capable of locking in place, a characteristic that is near impossible for a surgeon’s own arm. Intraoperative imaging with image-guided neuronavigation and robotics is frequently utilized as surgical adjuncts and must be accounted for when planning the operating room layout. This intraoperative utilization of technology, however, requires additional methodical preoperative planning. Image guidance navigation systems may be used for a variety of cranial or spinal procedures, and each case may necessitate specific preoperative or intraoperative imaging sequences. The timing of acquisition of these images in relation to the operation should be considered, as some patients may require earlier admission to obtain these sequences. Furthermore, when positioning a patient in the operating room, the surgeon should determine the appropriate orientation and exposure so that navigation or robotics can effectively be utilized without getting in the way of the surgeon.

Intraoperative CT scanning for image-guided spine surgery or functional neurosurgery requires confirmation of machine availability and appropriate radiography technician support. Intraoperative fluoroscopy is commonly used during spine or skull base procedures. Intraoperative MRI has been used in a variety of tumor cases and similarly requires preoperative setup and appropriate use of MRI-compatible equipment in the operating room. Intraoperative catheter angiography and fluorescein angiography are commonly used during cerebrovascular procedures, and operating rooms with fluoroscopy capabilities may have to be specially booked. Should cannulation of the femoral or radial artery for intraoperative angiography be required, the surgeon should take this into consideration when positioning the patient and discussing this with the entire surgical team before the operation.