Use of Regional Anesthesia in Patients with Multiple Sclerosis

the use of regional anesthesia. Specifically, patients with autoimmune mediated neurologic disorders. The selected pathophysiology of multiple sclerosis and regional anesthesia and their considerations via evaluation of research studies will be presented. Furthermore, suggestions for anesthesia care for these patients will be provided. Project Aim: The purpose of this article is to and educate anesthesia providers on patients with multiple sclerosis and anesthesia implications for this population. There appears to be a lack of discussion and research in the United States regarding the use of regional anesthesia in these patients. After reading this article, the reader will be able to identify patients at an increased risk of nerve damage, evaluate them properly preoperatively, and objectively determine if the patient is considered a candidate for regional anesthesia. Data The research information was gathered

evaluate the risks and benefits of using regional anesthesia and determine if the patient is a candidate. The reader will also have a better understanding of the pathophysiology of multiple sclerosis and its anesthetic considerations to improve quality of care and perioperative outcomes.

Pathophysiology of Multiple Sclerosis
Multiple sclerosis (MS) is an inflammatory autoimmune disorder of the central nervous system (CNS). However, recent post-mortem studies have reported some degree of peripheral involvement [3]. Although genetic susceptibility is likely, there is no obvious genetic, environmental or infectious cause that has been identified. Additionally, there is no clear understanding of the immunopathogenesis of the disorder that determines site of tissue damage, variations throughout history, or the severity of disability Pathologically, MS possesses a unique combination of characteristics that include inflammation, demyelination and axonal damage in the CNS; followed by the formation of plaques resulting in further alteration of nerve conduction [4]. The innate immune system is thought to play a major role in the initiation of multiple sclerosis by modification of T and B-lymphocyte function.
The adaptive immune system is also involved by activation of CD4 and CD8 cells. It is their polarization to Th1 and Th17 effector cells and cytokine formation that causes damage to the blood brain barrier. This allows autoreactive lymphocytes access to the CNS subsequently leading to the characteristic demyelination associated with the disease [3] (Figure 1).

Figure 1: Multiple Sclerosis.
Symptoms associated with MS are often varied with multifocal involvement, but there are two general clinical patternsexacerbating-remitting or chronic progressive. Progression of MS is caused by lack of remyelination and axonal degeneration which is irreversible and causes permanent neurological deficits [3]. Physical manifestations reflect the sites where demyelination has occurred. Although ascending spastic paresis of the skeletal muscles is often prominent, symptoms may also present as sensory deficits, autonomic dysfunction, emotional lability, bladder and bowel dysfunction and visual disturbances. MS exacerbations can be triggered by heat, stress, infections and pregnancy. Diagnosis of MS is made based on clinical features alone or in combination with oligoclonal immunoglobulin irregularities in the cerebrospinal fluid, prolonged latency of evoked potentials, and changes in white matter. There is currently no cure for MS and treatment is directed towards symptom control and slowing the progression of demyelination [4].  [5]. When appropriate for the procedure, the use of regional anesthesia may allow avoidance of neuromuscular blockade and associated complications. Prior to determining if a patient with MS is a candidate for regional or neuraxial anesthesia, a thorough preoperative assessment must be done. History and pattern of disease, physical and neurological deficits, especially those impacting the respiratory system, oxygen saturation, medications, and previous triggers should be appreciated [4]. Patients with significant respiratory compromise or cognitive dysfunction may notably benefit from the use of regional anesthesia. Additionally, the efficient and prolonged analgesia associated with regional anesthesia may contribute to a less stressful and painful postoperative period decreasing the risk of exacerbations [3]. concerns, epidural anesthesia is considered a safe alternative because the concentration of LA that approaches the subarachnoid space after an epidural injection is approximately one fourth of the epidurally administered concentration [3]., A main point of concern for anesthesia providers considering the use of regional anesthesia in this patient population is the proposed increased risk that the underlying condition may worsen, or a new deficit will develop. This phenomenon was first described in 1973 as the "double crush phenomenon" by Upton and McComas [1]. It was thought that a nerve with pre-existing neural compromise was more likely than a healthy nerve to incur damage at another point along the nerve. This is known as the double crush phenomenon, described by the photo below [1] (Figure 2). formation, ischemia from tourniquet use or constrictive dressings, or from regional anesthesia related risks such as mechanical trauma from needle placement or LA toxicity [1]. Historically, patients with pre-existing neurological disorders were not offered neuraxial techniques due to fear of worsening neurological deficits. For decades, this has been standard clinical management of these patients because of a recommendation made in 1956 by Dripps and Vandam [6] .This standard of practice was continued because of provider and patient biases as well as the high risk of medicolegal concerns [6]. Despite the fears surrounding double crush phenomenon related to regional and neuraxial anesthesia worsening symptoms in patients with MS, there are several factors such as hyperpyrexia, stress and infection that are known to negatively affect the disease progression or exacerbation [5].

The cause of decline in neurologic function in patients with MS
is not clearly understood and may simply be coincidental in the perioperative period regardless of the anesthetic technique used.
However, because of the difficulty in establishing cause of second crush during surgery, many providers continue to avoid regional anesthesia [1].

Discussion
Much of the literature evaluating the safety of regional anesthesia in patients with MS is contradictory and sparse. Few studies have been completed and, those that have, have primarily been retrospective chart analyses. Although there is a great need for further investigation on this topic for definitive recommendations, current data suggests that risks previously associated with neuraxial blockade in patients with neurologic disorders may be less frequent than believed in the past [1]. Hebl, Horlocker and Schroeder conducted a retrospective chart review from the Mayo Clinic, spanning over twelve years from 1988 to 2000 [7]. They examined the effects of 139 patients with a history of a central nervous system disorder that received a neuraxial block for a surgical procedure. Prior to neuraxial blockade, motor weakness was the most frequent neurologic deficit among patients. Of the considered contraindicated as it was previously thought to be The authors summarize that the decision to use neuraxial anesthesia techniques on patients with pre-existing neurologic disorders should be evaluated case by case and a thorough preoperative assessment is crucial. Many patients with advanced deficits affecting the respiratory and cardiovascular systems may benefit from the blunting of the sympathetic nervous system using regional techniques [7].  [8].
A case report by Koff and colleagues describes a severe brachial plexopathy after a interscalene nerve block for a total shoulder arthroplasty in a patient with MS [9]. Despite known benefits associated with regional anesthesia in patients undergoing joint replacement, use in the patient with MS is not definitive. Although MS is a disorder of the central nervous system, there is data supporting peripheral involvement in 4-14% of patients [10].
Postoperatively, the patient reported dense sensory and motor block and was comfortable for the first hour. The next day, the patient was experiencing 5/10 pain with persistent flaccid motor block of his entire right arm. A neurology consults and electro myelogram were ordered. A diagnosis of brachial neuritis was made, and high dose steroids were prescribed. On post-operative day 11, complete paresis of the right arm remained, and new electromyography showed active denervation of all muscles in the arm with no voluntary motor recruitment. At 3 months, the patient showed signs of reinnervation of the muscles of the arm.
However, after 8 months, the patient still had significant weakness in the right upper extremity, 50% loss of motion and visual atrophy of the arm as well as the pectoralis muscles of the right side [10].
Despite testing such as electromyography and MRI, it remains difficult to identify and differentiate an ethology when multiple factors were involved. Potential factors include direct trauma from the nerve block, neurotoxicity from LA, patient positioning such as extreme abduction and external rotation; all which can occur to any patient undergoing total shoulder replacement [11]. An additional confounding variable in diagnosing the cause of postoperative neurologic deficits in MS is that an exacerbation may be caused by many other non-traumatic factors such as hyperthermia, stress, and electrolyte abnormalities. Therefore, although the mechanism of this injury is not definitive, the pre-existing pathology of the peripheral nervous system may have been a contributing factor.
Authors conclude that the decision to perform peripheral nerve blocks must be made on a case by case basis, with an understanding that the peripheral nervous system may be somewhat involved in the pathology of MS [9].

Conclusion
While it is certain that surgical stress negatively impacts the patient with MS, there are no definitive studies on the long term or immediate implications of nerve blocks. Further research is needed in this area, but recent studies show promise for positive outcomes for these patients. Theoretically, regional anesthesia/ analgesia would reduce pain and stress associated with surgery thus reducing the risk of exacerbation. Nonetheless, the theory of double crush phenomenon must be considered. Much of the literature supports the use of peripheral nerve blocks and epidural anesthesia/analgesia and reports that MS should not be considered a contraindication to these pain control modalities. However, spinal anesthesia should still be avoided due to proximity to the CNS and high concentrations of LA to central lesions. The decision to proceed with regional anesthesia in the patient with MS must be made on a case by case basis and careful considerations must be made regarding the risks and benefits. It is important for the anesthesia provider to tightly control temperature and stress during the perioperative period to exclude those as causes of disease exacerbation. Although more research needs to be done for definitive recommendations, overall evidence supports the safety and efficacy of regional anesthesia in patients with MS and presence of the disease should not be considered an absolute contraindication.

Conflict of Interest
There is no economic or conflict of interest present by the author Disclosure I have no conflicts of interest

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