Published on 13/03/2015 by admin
Filed under Neurosurgery
Last modified 22/04/2025
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CHAPTER 25 Surgical Planning
Overview
Martin Weiss, Gabriel Zada, Alexander A. Khalessi
Comprehensive planning represents an axiomatic prerequisite for any neurosurgical procedure. “Failing to prepare is preparing to fail” holds particularly true in neurosurgical cases given the unforgiving nature of the human nervous system. Thorough preoperative consideration of the technical goals and potential pitfalls ensures the safest and most efficacious outcome for the patient. Effective planning allows the surgeon critical flexibility and latitude in managing deviations from the intended operative course. Indeed, the experience and ability to detect and handle the most adverse intraoperative events should be a goal for any surgeon. By taking the necessary steps to ensure adequate preparation for a case, the surgeon may prevent or avoid many significant neurosurgical complications.
Any surgical procedure demands a working preoperative diagnosis. Effective intervention requires a theoretical understanding of the pathophysiology involved or a directed effort to acquire further information. The surgical plan should therefore not only be based on a working diagnosis but also designed to accommodate changes in the operative plan as the case proceeds. Admittedly, even sound planning generates an incomplete preoperative state of information. Intraoperative findings or surgical pathology results, if anticipated, allow the reasoned pursuit of alternative surgical goals. Due consideration of nonsurgical diagnoses (e.g., prolactinoma, lymphoma) and alternative modalities (e.g., medical therapy, radiation therapy, radiosurgery) represents a crucial component of preoperative planning. Surgical planning thereby seamlessly blends with a larger treatment plan to minimize morbidity and optimize timely diagnosis and treatment of disease.
This chapter outlines a generalized approach to preoperative neurosurgical planning, emphasizing key considerations and adjunctive measures essential to optimization of patient outcomes beyond the incision.
Before any neurosurgical procedure, the surgeon must complete a comprehensive evaluation of the patient. Detailed history, physical examination, and review of the patient’s laboratory results and radiographic studies are paramount. Symptom time course and onset represent central features of the suspected disease and complement a focused neurological history. Pertinent negatives must be duly considered, and a strict accounting of preoperative deficits will be critical to establishment of a baseline with which to compare the patient’s postoperative examination findings. Moreover, inquiring about the side of hand dominance is significant in many cranial procedures. Further review of a patient’s past medical and surgical history, medications, allergies, and any pertinent social or familial considerations should be undertaken.
A complete review of systems is routinely performed. The physical and neurological examination should be performed soon before the procedure and documented in the medical chart. The complete neurological examination includes an assessment of mental status and speech ability, cranial nerve function (including the first cranial nerve), motor and sensory function, reflexes, and cerebellar and gait testing. Formal visual field and acuity examination may be indicated before selected cases if sellar or suprasellar disease exists. Rectal examinations for tone, volition, sensation, and the bulbocavernosus reflex may be necessary in instances of spinal disease. Other aspects of the patient’s overall medical status demand consideration in every case; many neurosurgical patients will have significant comorbidities requiring preoperative attention. The goals of surgery should always be considered as they relate to the patient’s overall medical status and personal preferences.
Routine laboratory values are indicated before any nonemergent surgical procedure and should be obtained to screen for a number of underlying systemic conditions that may pose a risk to a patient undergoing general anesthesia and surgery. A qualitative β-human chorionic gonadotropin assessment should be performed for every woman of childbearing age before surgery. Baseline renal function and electrolyte levels are determined and evaluated further as necessary. Any suggestion of infection, such as an elevated white blood cell count, positive cultures, elevated erythrocyte sedimentation rate, or elevated C-reactive protein level, should be considered, especially in elective cases or if hardware implantation is planned.
Underlying anemia must be worked up and corrected accordingly. Any suggestion of bleeding diathesis or coagulopathy should be investigated further and corrected. Preoperative laboratory investigations geared toward these issues include platelet count, prothrombin time (international normalized ratio), partial thromboplastin time, and bleeding time (if necessary). Many patients currently take anticoagulant or antiplatelet agents for a number of underlying medical comorbidities. Plans for discontinuation or reversal of these agents (or perhaps initiation of these agents in select endovascular cases) should be addressed at least 1 week before surgery.
Blood typing and screening, or crossmatching for reserve units and additional blood products, should be requested from the blood bank and verified in advance. If sellar disease exists, a full or selective endocrine panel is drawn to assess for deficiencies in any number of hormonal axes. The thyroid and cortisol axes are of paramount importance, and deficiencies must be identified and repleted before any surgical procedure is performed. Ruling out nonsurgical lesions, such as prolactinomas, additionally necessitates judicious review of preoperative laboratory work.
Preexisting cardiac disease is commonly encountered in the neurosurgical patient population. Preoperatively, patients should undergo a detailed cardiovascular history to assess exercise tolerance and to screen for angina or congestive heart failure. Should there be preexisting disease or if a patient has significant risk factors, clearance or risk assessment from a cardiologist may be required before an elective case. A 12-lead electrocardiogram and plain chest film are obtained in the majority of adult patients before routine surgery. If further cardiac work-up is indicated, exercise treadmill testing, echocardiography, nuclear medicine study, or coronary angiography may be performed to further assess the degree of cardiac risk.
Hypertensive patients require adequate blood pressure control on multiple visits before undergoing general anesthesia for an elective case. In general, any cardiac condition that poses a risk to the patient’s overall condition should be addressed before an elective neurosurgical procedure. The degree of cardiac risk, if present, must always 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, and include invasive cardiac monitoring and perioperative medications. In the setting of baseline anemia or anticipated blood loss, large-bore intravenous access is critical to the timely delivery of blood products and prevention of a hypovolemic intraoperative insult.
Baseline pulmonary disease is also encountered frequently in the general neurosurgical population. Comorbidities such as asthma and chronic obstructive pulmonary disease may limit optimal provision of anesthesia during a neurosurgical case and should be addressed with a thorough preoperative evaluation. Historical details, including a smoking history, merit special attention by the physician. A plain chest radiograph, pulmonary function tests, and chest computed tomographic scans are within the battery of tests that may be indicated for preoperative work-up. Once again, perioperative medications, including steroids and beta agonists, may be indicated for patients with pulmonary disease and should be discussed with the anesthesia staff. Instances involving severe ventilatory compromises may limit positioning options (i.e., protracted prone positioning), and coincident structural lesions (i.e., lung masses) may dictate the laterality of the neurosurgical approach to midline structures.
Some neurosurgical patients will present with malnutrition or failure to thrive in relation to their disease process. Many afflictions prevalent in the population of neurosurgical patients render them unable to tolerate a normal diet. Because of their mental status, paralysis, or any number of airway or cranial nerve issues, some patients rely on alternative sources of nutritional intake. These may include nasogastric tubes, percutaneous gastric tubes, and parenteral routes of intake for nutritional supplementation. Before any neurosurgical case, a patient’s nutritional status should be considered and optimized. A serum prealbumin level can be monitored to assess and observe a patient’s nutritional status. A consultation with a nutritionist can be invaluable in optimizing a patient’s status before major surgery. Patients who have undergone previous surgery or radiation therapy or those receiving chronic steroid treatment may present additional wound healing concerns that require additional preoperative planning to achieve adequate wound healing. Diabetes, especially in the setting of poor glycemic control, may further compromise wound healing. Hemoglobin A1c levels may be used to screen for this clinical scenario. In certain situations, specialized tissue transfer techniques, such as rotational pedicle-based vascular flaps or free flaps, are required, often in conjunction with a separate team of specialty surgeons.
Once a complete evaluation of a patient’s neurologic and systemic disease has been thoroughly considered and a surgical plan formulated, a frank discussion with the patient and any other individuals involved in the patient’s care should take place. The goals of surgery and potential barriers to the achievement of these goals should be clearly and honestly delineated. For nonemergent cases, the benefits and risks of the recommended procedure and its alternatives are reviewed, and any additional questions are answered by the surgeon. Informed consent should be obtained before the initiation of any nonemergent procedure. The consent process includes information about the placement of any permanent implants or hardware that may be used as well as the potential for the transfusion of blood products if necessary.
Before the initiation of any surgical procedure, the correct array of radiographic imaging is obtained and reviewed thoroughly by the surgeon. Consultation with a neuroradiologist may be beneficial in select cases. Preoperative images frequently include plain films, computed tomographic imaging, magnetic resonance imaging, angiography, and a variety of additional modalities. The surgeon should ensure that the correct sequences have been performed and reviewed before the case. The images should be available to the surgeon for the duration of the procedure. In addition to static images, dynamic studies such as flexion-extension views may provide insight into the responsible pathologic process. Certain pathologic entities involve abnormalities of flow, which make dynamic studies (i.e., assessment of flow in an arteriovenous malformation) important in the preoperative evaluation.
Intraoperative imaging and image-guided neurosurgery are increasingly used surgical adjuncts that require additional preoperative planning steps. Image guidance navigation systems may be used for a variety of neurosurgical cases and require particular preoperative imaging sequences. The timing of image acquisition in relation to the operation should be considered, as some patients require early admission for these sequences to be obtained. Intraoperative fluoroscopy is commonly used during select spine or skull base cases and is set up before the case. Intraoperative magnetic resonance imaging has been used during the past decade or so in a variety of tumor cases and requires specific steps for preoperative setup and preparation of instrumentation. Intraoperative angiography and fluorescein angiography are commonly used during cerebrovascular cases and also require prior planning. Cannulation of the femoral artery and initial imaging for intraoperative angiography are frequently performed and set up before the operative portion of the case.
Before the initiation of the surgical procedure, the surgeon should review the operative plan with the anesthesia team. Optimal physiologic parameters (blood pressure, volume, temperature) and any additional methods of monitoring required during the procedure should be reviewed. The proper use of ventriculostomy and lumbar drain catheters should be reviewed before surgery when these modalities are to be used. In pediatric cases or other cases in which the degree of bleeding is of paramount concern, a plan for monitoring and repletion of blood or any additional products should be in place. Planning for autologous blood recovery systems or normovolemic hemodilution may be undertaken when a significant degree of bleeding is anticipated.
Particular requirements for the administration of anesthetic medications for induction and the duration of the case should be reviewed with the anesthesiologists, including the selection of paralytic agents or total intravenous anesthesia. This is of key importance when neurophysiologic monitoring will be performed. Plans for electroencephalographic burst suppression must also be discussed with the anesthesia team before the surgery. In certain functional and tumor cases, neuroleptic anesthesia is desired to assess the patient during the procedure. Anesthesia for awake craniotomy or deep brain stimulator placement requires additional preparation on the part of the anesthesia team, and the timing and depth of anesthesia must be preplanned. The perioperative administration of medications such as antibiotics, steroids, hemostatic or anticoagulation agents, and antiepileptic drugs is frequently indicated and discussed with the anesthesia team, in addition to affirmation of the side or site of surgery in a formal “time-out” procedure. A review of a patient’s allergies should be readily available and alternative medications selected for existing conflicts.
Any concerns about spinal stability should be noted before positioning and intubation. Fiberoptic intubation may be required in instances of cervical instability or spondylosis, in which the extension required for standard intubation places the neural elements at risk. Certain surgical positions require additional means of patient monitoring, which are planned before surgery. A typical example of this is the requirement for central venous Doppler monitoring for air emboli in the case of sitting craniotomies. Notably, the use of the Mayfield skull clamp in cranial cases and posterior cervical cases allows stable head fixation. Somatosensory and motor evoked potential baselines before and after final positioning further confirm safe preparation and manipulation of the patient before definitive surgical intervention.
In general, the selected surgical approach allows the most direct and maximal access to the pathologic process, with minimal morbidity to surrounding structures. Any surgical instrumentation that may be required to perform the operation should be requested and tested before initiation of the procedure. Vascular lesions require detailed consideration of flow dynamics and proximal control in preparation for a bleeding event. Likewise, surgical manipulation generally minimizes traction or compression of nervous structures. For instance, resection of extra-axial tumors is thereby best accomplished by mobilization out and away from adjacent nervous structures.
For cranial procedures, the surgical approach and position should be planned and any equipment for positioning set up in advance. This may include devices for cranial fixation and for positioning the body or extremity support. If surgical navigation is to be used, it should be set up, registered, and verified before the procedure begins. Neurophysiologic monitoring, such as somatosensory, motor, or brainstem auditory evoked responses, must be anticipated and discussed with the anesthesia and neuromonitoring teams before surgery. The method of visualization to be used for the procedure, such as the operating microscope, surgical loupes, or an endoscopic system, should be selected and tested before surgery. Any adjunctive measures for brain relaxation, such as placement of a ventriculostomy catheter or lumbar drain, should be considered in advance. Drill equipment, including electric or pneumatic setup, and any additional drill bits or attachments should be selected and tested. Instruments or products required for hemostasis, such as monopolar and bipolar cautery, collagen sponge, Surgicel, and thrombin, should be discussed with the operating room staff before surgery so that they are ready for use at the onset of the case.
Before craniotomy procedures for neoplastic diseases, a surgeon should have a working diagnosis and a plan prepared. If a biopsy procedure is to be performed, the method of acquisition is planned in advance. This may be done by stereotactic frame-based procedures, image-guided neuronavigation through a bur hole or open craniotomy, or direct open biopsy. The surgical pathologist should be notified and on standby before the initiation of surgery. A plan is prepared in advance as to how the case should proceed after initial assessment of the frozen biopsy specimen. A surgeon should plan for a variety of scenarios, depending on the results of the biopsy. In certain cases, complete tumor resection is indicated. In other cases, partial resection, decompression, or palliation is attempted. Other biopsy results may suggest a medically treatable condition, and the decision to terminate surgery may be made at that time. Tumors that appear especially vascular on imaging studies may require preoperative neurointerventional embolization. Instruments required for tumor resection are anticipated and may include special transsphenoidal or skull base instrument sets, endoscopic equipment, and the Cavitron ultrasonic aspirator. If the potential for a cerebrospinal fluid leak near the skull base exists, the abdomen may be prepared for a fat or fascial graft harvest. Injection of fluorescein dye into the subarachnoid space may be warranted to improve detection of a cerebrospinal fluid leak and should be done before positioning.
The surgical management of complex cerebrovascular disease can often be greatly facilitated by thorough preoperative planning. When possible, an approach is selected that offers exposure of the entire lesion and proximal vasculature. Preparation for a potential intraoperative aneurysm rupture is a requirement, and a plan must be established in relation to when in the procedure this event occurs. Additional steps to achieve proximal vascular control of cerebral aneurysms and arteriovenous malformations are frequently mandated. Methods of proximal control include temporary aneurysm clipping, intraoperative balloon occlusion, and exposure of proximal vessels in the neck. If necessary, a balloon test occlusion is performed in advance to ascertain whether a given vessel can be sacrificed. In cases of anticipated reconstruction or bypass procedures, preoperative studies are performed to ensure that feeder and recipient vessels are sufficient, and mapping of the vessel course with a Doppler instrument may be required. In cases in which no feeding vessel is accessible, a venous or arterial graft harvest site may be selected and prepared on the basis of the flow demand of the target distribution. Intraoperative angiography may be used for a variety of reasons during cerebrovascular cases, including proximal control, suction-decompression, and assessment of persistent filling of vascular lesions and parent vessels. Indocyanine green fluorescence angiography is an alternative measure that can be used intraoperatively to assess the distribution of cerebral blood flow. A wide variety of aneurysm clips should be available to the surgeon to treat complex aneurysms, including various sizes and configurations of straight and fenestrated clips. Temporary and permanent aneurysm clips should be readily available in the event of an intraoperative rupture. Verification of distal artery patency after aneurysm ligation can be performed with a micro-Doppler flow probe, fluorescence or intraoperative angiography, or an endoscope.
For spine cases, the surgical approach must also be selected, and equipment required for positioning should be ready. This may include a standard radiolucent surgical table or the Jackson surgical table. The Wilson frame may be desirable in a variety of cases to induce flexion to facilitate intralaminar access. Equipment to perform imaging for surgical localization, such as plain radiography, fluoroscopy, or image-guided navigation systems, should be available. Monitoring of somatosensory and motor evoked potentials, if desired, is set up before the case is started. Additional instrumentation for exposure, stabilization, and fusion should be sterilized and prepared for the case. This may include retractor sets, dilator sets, and any combination of grafts, plates, screws, and rods that may be required to complete the case. When a bone fusion is desired, the surgeon should have a plan for use of autograft, allograft, or any number of additional fusion products available. If iliac crest graft harvesting is required, this should be planned and the field prepared preoperatively.
The complexity of neurological surgery demands the employment of all means and methods available to the surgeon to maximize the safety of the patient and to enhance the surgical procedure. Surgical success therefore begins well before setting foot in the operating theater. In the patient’s history, in the laboratory work-up, in review of the radiographic findings, and in an appraisal and discussion of the risks and a tempering of expectations, the foundation for the operative enterprise is built. The goal is to use a team familiar with the necessary operative equipment, with a reliance on other disciplines to enable a plan of care to facilitate the likelihood of a successful intervention. Neurosurgery will always remain among the most audacious of human endeavors; preoperative planning provides the footing to help patients and diminish the burden of neurological disease.
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