Performing regional anesthesia in patients with preexisting neurologic or neuromuscular disease remains controversial and presents a special challenge to anesthesiologists. Historically, regional anesthesia has been relatively contraindicated in these patients for fear of worsening neurologic outcomes [1]. In addition, many practitioners may be reluctant to provide regional anesthesia to these patients due to medicolegal concerns. Factors contributing to this belief include local anesthetic toxicity to neurons, ischemia secondary to additives such as epinephrine, and injury to nerves from direct needle trauma. Upton and McComas described the “double crush” phenomenon which suggested that patients with nerve injury are more susceptible to nerve damage at another site [2]. Other studies appear to not only support the double crush phenomenon but suggest that the cumulative or dual injury to the nerve is greater than the expected additive damage that one might expect [3]. Thus, placing nerve blocks in patients with preexisting nerve injury may theoretically increase their risk of further injury. In addition, local anesthetic and additives in blocks may cause a subsequent injury to nerves based on their neurotoxic properties. In fact, studies evaluating the toxicity of local anesthetic and additives that have been conducted in animal models suggest that nerve injury is possible [4–6]. Therefore it may be prudent to minimize the dose or avoid local anesthetics in some patients.

Numerous studies or case reports describe the successful use of regional anesthetic techniques in a variety of neuromuscular disorders including multiple sclerosis, post-polio syndrome, amyotrophic lateral sclerosis (ALS), muscular dystrophies, myotonias, and others [7, 8]. These large studies are retrospective in nature and provide some evidence of the safety of regional anesthetic techniques in such patients. However, prospective randomized studies are not likely to be conducted due to the relative infrequency of patients with these disorders presenting for surgery. Specific guidelines regarding the use of regional techniques in the setting of neurologic disease are difficult to define because of these limitations. Therefore, the goal of this chapter is to review several of the more common neurologic disorders that an anesthesiologist may encounter and outline what information currently exists to help guide the use of regional anesthesia. The use of a regional anesthetic technique along with careful use of local anesthetics in terms of concentration and dose should be made in all patients but especially in patients with preexisting neurologic disorders [9].

Evaluation of the patient with neuromuscular disease must consider not only the neuromuscular derangements, but also the secondary effects the disease may have had on other organ systems, particularly respiratory and cardiovascular. These secondary effects may have a significant impact on the administration and course of both general and regional anesthesia in these patients. In many cases, it may be advantageous to utilize a regional anesthetic technique. Evaluation and careful documentation of preexisting neurologic deficits is a vital part of the preoperative anesthesia workup for any patient with an underlying neurologic disorder. This is imperative whether regional or general anesthesia is planned. Changes in neurologic status are frequently seen in the perioperative period in these patients, and the documentation of preexisting deficits facilitates the interpretation of any changes seen postoperatively.

The patient with neuromuscular disease may be at risk for respiratory compromise in the perioperative period. In particular, impaired ventilatory reserve with reduced ability to respond to hypercapnia and hypoxia may result in an increased risk of respiratory failure [10, 11]. The site of surgical incision affects the risk of respiratory complications, with a higher incidence in patients undergoing upper abdominal and thoracic procedures. The method of perioperative analgesia may have a significant influence on this risk of respiratory compromise, providing the anesthesiologist with an opportunity to positively influence the patient’s course.

In addition to hypoventilation, dysfunction of the pharyngeal muscles and the potential of aspiration add to the possibility of pneumonia postoperatively. Maintenance of an awake patient using a regional technique can only aid in the prevention of aspiration. In contrast, an endotracheal tube can be protective at the expense of further loss of muscle tone of both the respiratory and pharyngeal muscles . Finally, patients with severe neurologic disorders may have a component of restrictive lung disease which places them at higher risk for pulmonary complications during mechanical ventilation [12]. Preoperative assessment of respiratory function is an essential component of the preoperative evaluation.

Similarly, the cardiovascular effects of neuromuscular disorders must also be considered in the preoperative evaluation. Autonomic dysfunction occurs with many neurologic disorders and constitutes the major contributor to complications related to this organ system. ALS, Guillain–Barré syndrome, multiple sclerosis, and spinal cord lesions above the level of T6 can all have alteration of the autonomic nervous system. Several findings in the preoperative evaluation may guide the clinician to an increased suspicion for the presence of autonomic dysfunction. The absence of beat-to-beat heart rate variability with deep breathing is one of the most sensitive signs of autonomic dysfunction. Additional characteristic signs include resting tachycardia, orthostatic hypotension, cardiac dysrhythmias, and impotence. Because of the presence of autonomic dysfunction, these patients are at risk for cardiac conduction abnormalities and wide fluctuations in blood pressure. Required avoidance of oral intake makes the presence of relative hypovolemia common. A sympathectomy from neuraxial blockade, but potentially a variable amount from narcotics and inhalational anesthetics as well, can result in exaggerated hypotension in this setting. Finally, unexpected intraoperative cardiorespiratory arrests have been reported in patients with autonomic dysfunction which is second in frequency only to respiratory failure [8, 9].

Myocardial dysfunction and arrhythmias caused by changes in the cardiac muscle and conduction pathways are associated with numerous myopathic diseases including the muscular dystrophies, Guillain–Barré syndrome, and polio. A high index of suspicion must be maintained in the preoperative evaluation of these patients, as exercise tolerance is likely to be very limited by underlying neuromuscular disease.

Multiple sclerosis is an acquired central nervous system disease characterized by multiple sites of demyelination primarily in the brain and spinal cord. Multiple sclerosis was once thought to spare the peripheral nervous system; however, emerging evidence suggests that peripheral neuropathy can result as well [13, 14]. Demyelination of axons results in a slowing of sensory and motor conduction which leads to widely variable clinical signs and symptoms specific to the sites of demyelination. MS typically begins in early adulthood and affects women more than men. It has a variable prognosis and up to 50 % of patients may require assistance with ambulation within 15 years of diagnosis [15]. Symptoms most commonly include fatigue, visual disturbances, gait disturbances and incoordination, numbness and tingling, weakness, depression, and bowel/bladder incontinence [16].

The diagnosis of multiple sclerosis is made on clinical criteria with support from laboratory data such as cerebral spinal fluid analysis showing oligoclonal bands and repeated magnetic resonance images with findings of multifocal lesions of differing ages. Supportive information may be gained from evoked potential studies with visual, brainstem, and somatosensory potentials revealing slowed conduction [15].

The clinical course of multiple sclerosis is variable in nature and can include several forms with different phenotypes. The two main types of MS include relapsing-remitting disease or progressive disease. Eventually residual symptoms begin to persist between relapses. Extreme variability is seen among individuals, and the waxing and waning course makes it difficult to evaluate the effects of therapeutic interventions. Treatment with corticosteroids is often used to treat relapses. Other treatments include Interferon β, glatiramer acetate, immune globulin, mitoxantrone hydrochloride and plasma exchange but these may not change the long-term course of the disease.

The exacerbating factors of stress, fatigue, changes in temperature, and infection are associated with the perioperative period for more than one reason [17]. Delineating the natural course of the disease from the exacerbations due to surgery and anesthesia can be difficult. The purported effects of anesthesia on the course of multiple sclerosis continue to be controversial. However, it is the one neurologic disease that has the most information about the effects of regional anesthesia particularly in the obstetric population. Because of a continuing lack, or perceived lack of evidence, there is reluctance to utilize a regional technique in patients with multiple sclerosis, especially when considering epidural or spinal anesthesia.

Many of the studies and case reports available involve obstetric patients with multiple sclerosis, which constitutes a subset of patients likely to be considered for regional anesthesia. The natural history of multiple sclerosis in pregnancy is characterized by remission during gestation [18, 19] because of a presumed immunomodulatory protective effect [20]. This is also seen in other parturients with other autoimmune disorders such as rheumatoid arthritis. In fact, patients who have had a full-term pregnancy have a tendency toward an increased time interval to sustained disability. Patients are likely to have more multiple sclerosis relapses in the first 3 months postpartum regardless of whether they received an epidural [20].

Neuraxial, and in particular spinal, anesthesia has been implicated as a potential [21] cause of exacerbations in these patients even though contradictory retrospective studies and case reports exist [22, 23]. Theories to explain any exacerbation of multiple sclerosis symptoms by spinal anesthesia , focus on the potential for an increased susceptibility of demyelinated areas of nerves to the neurotoxic effects of local anesthetics [22]. The three to four times higher concentration of local anesthetic reaching the spinal cord white matter with subarachnoid as opposed to epidural anesthesia could explain the higher risk of exacerbation posed by this modality [24]. Schapira [24] demonstrated that diagnostic lumbar puncture alone did not appear to induce relapses in patients with multiple sclerosis, lending support to the theory that any effects of spinal anesthesia on multiple sclerosis are related to local anesthetic neurotoxicity. In addition, intrathecal morphine has also been used successfully without exacerbation anecdotally in patients with multiple sclerosis.

Bader et al. [22] performed a retrospective and partially prospective review of all obstetric multiple sclerosis patients at the Brigham and Women’s Hospital between 1982 and 1987 and noted no significant difference in exacerbation rates between patients receiving epidural anesthesia and local infiltration for vaginal delivery. The total number of pregnancies in patients with multiple sclerosis in this study was 32. However, all of the women who did experience a relapse within 3 months postpartum had received epidural anesthesia with a concentration of bupivacaine greater than 0.25 %. This was a total of three patients. The authors proposed that the use of higher bupivacaine concentrations over a longer period of time (i.e., labor epidurals) may affect the rate of postpartum multiple sclerosis relapse, particularly if multiple local anesthetic boluses are required. Warren et al. [25] also reported minor exacerbations in a patient following two separate epidurals (years apart) for vaginal delivery although a relatively large total dose of bupivacaine was used on the second occasion only. Of note, although these incidents suggest that local anesthetics may potentially produce neurologic symptoms in demyelinated areas of patients with multiple sclerosis, these effects have not been permanent and generally gradual recovery over time is the rule [26].

Despite these concerns, there are many reports of successful use of epidural anesthesia in multiple sclerosis patients without evidence of relapse. Capdeville and Hoyt [27] performed a retrospective review of all obstetric patients with multiple sclerosis admitted to University Hospitals of Cleveland from 1986 to 1993. Over this 7-year period, eight women with multiple sclerosis underwent eight vaginal deliveries, one cesarean delivery, and five obstetric-related procedures. The anesthetic techniques used were five epidurals, two general anesthetics, one pudendal block, and one narcotic technique. Only two exacerbations of multiple sclerosis were noted by chart review. One of these occurred after a general anesthetic, and the other was noted in a patient receiving a pudendal block. No exacerbations were seen in patients receiving epidural anesthesia. Confavreux et al. evaluated 254 women with MS and 256 pregnancies in 12 European countries [28]. They confirmed that the rate of relapse during pregnancy is reduced and found a relapse rate of 1.2 per woman per year in the first 3 months postpartum. They found that epidural anesthesia had no adverse effect on the rate of relapse. In a 2-year postpartum analysis of this study, this was also confirmed that epidural anesthesia did not have an effect on the relapse rate. The authors though state that the study was not designed to assess this risk specifically [29].

Crawford et al. [23] documented only one perioperative relapse in 50 non-obstetric and seven obstetric patients with multiple sclerosis receiving lumbar epidural anesthesia. In another series involving urologic surgery 14 spinal anesthetics were utilized with only one case of transient worsening of symptoms similar to patients receiving general anesthesia [30]. Again, the numbers are too small to lead to generalized recommendations but do indicate anecdotal success without complication involving the use of neuraxial anesthesia in patients with multiple sclerosis.

A significant concern in patients with multiple sclerosis is the presence of autonomic dysfunction and the potential for chronic hypovolemia in these patients, especially when considering employing a neuraxial technique. Episodes of marked hypotension with epidural and spinal anesthesia in MS patients with a reduced response to intravenous fluids and vasopressor therapy have been reported [31]. Racosta et al. performed a meta-analysis on cardiovascular autonomic dysfunction in MS looking at 16 studies with 611 patients and concluded that there was a wide variation in diagnosis and that using one abnormal autonomic test compared to at least two dropped the diagnosis rate from 42.1 to 18.8 % [32]. They also concluded that consensus is needed to define autonomic dysfunction in this patient group [33]. Regardless of the criteria used, autonomic dysfunction is present in many MS patients and meticulous preoperative evaluation needs to be completed when considering a regional technique.

The use of regional anesthesia in patients with multiple sclerosis can be safely conducted but can be controversial with some techniques particular with spinal anesthesia. Multiple case reports support its successful use, particularly in obstetric patients. Other case reports suggest a risk of perioperative symptom exacerbation and hemodynamic instability. If regional anesthesia is considered, the risk and benefits must be fully discussed with the patient. Special note during these discussions must be made of the potential for exacerbations of multiple sclerosis related to stress and temperature changes associated with the perioperative period regardless of the anesthetic technique used. In addition, parturients have a particular issue with increased incidence of multiple sclerosis relapse early in their postpartum period regardless of epidural use.

Amyotrophic Lateral Sclerosis (ALS) is a degenerative disease of the upper and lower motor neurons involving the brainstem and multiple spinal cord regions. There are multiple phenotypes such as bulbar presenting with speech and swallowing difficulties, limb-onset with combination of upper motor neuron (UMN) and lower motor neuron (LMN) signs in the limbs, primary lateral sclerosis with only UMN involvement, and progressive muscular atrophy with only LMN involvement [34, 35]. The etiology remains unclear, and the disease affects males more than women with lifetime risk for men of 1:350 and for women of 1:400 with peak age of onset of 58–63 for sporadic disease and 47–52 for familial disease [35].

The clinical features of ALS involve progressive muscular atrophy with weakness and fasciculations of skeletal muscles. Bulbar muscle weakness often predominates with an associated risk of aspiration. A characteristic emotional lability and frontal lobe type cognitive dysfunction is seen [34, 35]. Autonomic nervous system dysfunction is common with the associated risk of exaggerated hemodynamic responses during anesthesia. Death from myocardial or respiratory failure ensues, often within 6 years of the onset of symptoms.

Epidural anesthesia has been successfully used in patients with ALS. Kochi et al. reported three cases in which lumbar epidural anesthesia was used, emphasizing the advantage of avoiding tracheal intubations [36]. Combined spinal epidural has also been successfully used for femur fracture in a woman with ALS and significant respiratory compromise due to ALS. Sertoz and Karaman utilized a lumbar plexus and a sciatic block in this patient with ALS and a collum femoris fracture in order to avoid general anesthesia [37]. Finally, a report of paravertebral block for breast surgery was reported by Agnoletti et al. [38]. Regional techniques can be advantageous in this patient population as any duration of mechanical ventilation could accelerate the loss of muscle tone, and weaning from the ventilator could be quite a challenge. However, a high epidural or spinal block as well as epidural spread from a PVB can affect muscle function with detrimental effects in patients with severe restrictive lung disease and minimal ventilatory reserve.

Spinal cord injury has classically been divided into two distinct stages. Initial injury is classified as spinal shock which consists of a 1- to 3-week period of flaccid paralysis including loss of sensation temperature regulation, and spinal cord reflexes below the level of injury [39]. Hypotension, bradycardia, and changes in the electrocardiogram (premature ventricular contractions, nonspecific ST-T wave changes) are characteristic. Regional anesthesia is not frequently used during this stage of spinal shock because of the evolving neurologic injury. There is also a risk of hemodynamic instability as well as hypothermia.

The chronic stage of spinal cord injury is characterized by skeletal muscle spasticity and the return of spinal and autonomic reflexes below the level of injury. Autonomic hyperreflexia is seen in approximately 85 % of patients with lesions at or above T6. In this setting, a reflex response may be produced by a cutaneous (incision) or visceral (bladder distension, uterine contraction) stimulus below the level of injury. This afferent stimulus activates preganglionic sympathetic nerves, resulting in severe hypertension because of intense vasoconstriction below the level of the lesion. Under normal conditions, this response is modulated by inhibitory impulses from higher central nervous system centers. With a spinal cord lesion, this inhibitory input is lost and the vasoconstriction proceeds unimpeded. The resulting hypertension stimulates the carotid sinus baroreceptors, leading to reflex bradycardia and vasodilation above the level of injury [39].

Prevention and early treatment of autonomic hyperreflexia is critical. Both general and regional anesthesia have been used effectively. Broecker et al. noted that spinal and epidural anesthesia were logical choices to prevent autonomic hyperreflexia because the afferent limb of the reflex would be blocked [40]. Spinal anesthesia has been shown to be particularly useful [41], but epidural blocks are less reliable [40]. Parturients at risk for autonomic hyperreflexia from uterine contractions are likely to benefit from the early use of continuous lumbar epidural analgesia after the onset of labor [42]. In addition to its prophylactic use, regional anesthesia has been used therapeutically in patients with autonomic hyperreflexia [42].

Concerns often raised regarding the use of spinal anesthetics in this group of patients with spinal cord injury include potential difficulty in placement, difficulty in control or examination of block level, difficulty in evaluating for complications, and a potential increased risk of hypotension [43]. Lambert et al. performed a retrospective review of 78 procedures in 50 spinal cord-injured patients considered “at risk” for autonomic hyperreflexia [41]. No significant differences were seen in intraoperative blood pressure between those receiving spinal or general anesthesia. Both techniques seemed to protect equally against intraoperative hypertension. Several other studies describe successful use of neuraxial anesthesia for treatment or prevention of autonomic hyperreflexia.

Peripheral regional techniques can be utilized in patients with spinal cord injuries but present unique challenges as well. Interscalene or supraclavicular blocks can result in temporary phrenic nerve paralysis and can worsen respiratory function in patients that have compromised respiratory dynamics. Placement of peripheral blocks should utilize ultrasound technique as nerve stimulation may be altered in these patients in addition to potential altered anatomy.