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47: Degenerative Neurologic Diseases and Neuropathies

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CHAPTER 47 Degenerative Neurologic Diseases and Neuropathies

James Duke, MD, MBA

1 What is amyotrophic lateral sclerosis and its anesthetic considerations?

Also known as Lou Gehrig’s disease, amyotrophic lateral sclerosis (ALS) is a disease of both upper and lower motor neurons. It usually affects men in the fourth or fifth decade of life. Patients with ALS develop progressive weakness and eventually die (from pneumonia and pulmonary failure), often in a 3- to 5-year period. Although extremities are involved first, eventually bulbar muscles become affected, increasing the risk of aspiration. The pathogenesis is poorly understood but thought to be caused by mutations in the superoxide dismutase-1 gene. Treatment options are limited.

Reports of anesthetic difficulties are anecdotal. There is no evidence that either regional or general anesthesia exacerbates the disease. Succinylcholine-induced hyperkalemia and subsequent cardiac arrest have been reported. Nondepolarizing muscle relaxants have a prolonged duration of action. Aspiration is an increased risk, as is the need for postoperative ventilatory support. These patients are not at risk for malignant hyperthermia.

2 Review the clinical manifestations of Guillain-Barré syndrome

Acute idiopathic polyneuritis (Guillain-Barré syndrome) is currently the most frequent cause of generalized paralysis and usually presents with sudden onset of weakness or paralysis, typically in the legs, that spreads to the trunk, arms, and bulbar muscles over several days. Bulbar involvement may be suggested by facial muscle weakness. Areflexia is also a feature. Respiratory failure requiring mechanical ventilation occurs in 20% to 30% of cases. About half of all cases are preceded by a respiratory or gastrointestinal infection; and the pathogenesis is thought to be autoimmune, possibly related to similarites between bacterial liposaccharides and axonal gangliosides. Recovery may occur within weeks, although some residual weakness remains secondary to axonal degeneration. Mortality (3% to 8%) typically results from sepsis, adult respiratory distress syndrome, pulmonary embolism, or cardiac arrest. Plasmapheresis and immunoglobulin therapy result in some improvement, whereas glucocorticoid supplementation does not.

3 How is the autonomic nervous system affected in Guillain-Barré syndrome?

Autonomic dysfunction is a common finding. Patients may experience wide fluctuations in blood pressure, profuse diaphoresis, peripheral vasoconstriction, tachyarrhythmias and bradyarrhythmias, cardiac conduction abnormalities, and orthostatic hypotension. Sudden death has been described.

4 What are the major anesthetic considerations for patients with Guillain-Barré syndrome?

Patients may not handle oral secretions well because of pharyngeal muscle weakness and have respiratory insufficiency secondary to intercostal muscle paralysis. Aspiration is a risk. Secondary to autonomic dysfunction, compensatory cardiovascular responses may be absent, and patients may become hypotensive with mild blood loss or positive-pressure ventilation. Alternatively laryngoscopy may produce exaggerated increases in blood pressure. The response to indirect-acting vasoactive drugs may also be exaggerated. Because of the unpredictable and wide swings in blood pressure, intra-arterial monitoring should be considered. There is no evidence that either general or regional anesthesia worsens the disease.

Since Guillain-Barré syndrome is a lower motor neuron disease, succinylcholine is contraindicated because of the potential for exaggerated potassium release. Pancuronium should also be avoided because of its autonomic effects. Postoperative ventilation may be necessary because of respiratory muscle weakness.

5 Review the pathophysiologic features of Parkinson’s disease

Parkinson’s disease, an adult-onset degenerative disease of the extrapyramidal system, is characterized by the loss of dopaminergic neurons in the basal ganglia. With the loss of dopamine, there is diminished inhibition of the extrapyramidal motor system and unopposed action of acetylcholine.

6 Describe the clinical manifestations of Parkinson’s disease

Patients with Parkinson’s disease display increased rigidity of the extremities, facial immobility, shuffling gait, rhythmic resting tremor, dementia, depression, diaphragmatic spasms, and oculogyric crisis (a dystonia in which the eyes are deviated in a fixed position).

7 What are the effects of levodopa therapy, particularly on intravascular volume status?

Levodopa, the immediate precursor to dopamine, crosses the blood-brain barrier, where it is converted to dopamine by a decarboxylase enzyme. Treatment with levodopa increases dopamine both in the central nervous system and peripherally. Increased levels of dopamine may increase myocardial contractility and heart rate. Renal blood flow increases, as does glomerular filtration rate and sodium excretion. Intravascular fluid volume decreases, the renin-angiotensin-aldosterone system is depressed, and orthostatic hypotension is a common finding. High concentrations of dopamine may cause negative feedback for norepinephrine production, which also causes orthostatic hypotension.

8 Review the anesthetic considerations for a patient with Parkinson’s disease

image Abrupt withdrawal of levodopa may lead to skeletal muscle rigidity, which interferes with adequate ventilation. Levodopa should be administered on the morning of surgery and restarted after surgery.
image Extremes of blood pressure and cardiac dysrhythmias may occur.
image Phenothiazines (e.g., chlorpromazine, promethazine, fluphenazine, prochlorperazine) and butyrophenones (e.g., droperidol and haloperidol) may antagonize the effects of dopamine in the basal ganglia. Metoclopramide inhibits dopamine receptors in the brain. These medications should be avoided.
image Patients may be intravascularly volume depleted; therefore aggressive administration of crystalloid or colloid solutions may be required in the setting of peri-induction hypotension.

9 What are the clinical signs and symptoms of Alzheimer’s disease?

Alzheimer’s disease accounts for most of the severe cases of dementia in the United States. The disease follows an insidious onset, with progressive worsening of memory and decreased ability to care for oneself and manage the usual activities of daily life.

10 What is the most significant anesthetic problem associated with Alzheimer’s disease?

The inability of some patients to understand their environment or to cooperate with health care providers becomes an important consideration. Sedative drugs may exacerbate confusion and probably should be avoided in the perioperative period. Regional techniques may be used with the understanding that the patient may be frightened or confused by the operating-room environment. Reductions in the level of volatile anesthetic or opioid administered may be of benefit. A lack of cooperation and unanticipated outbursts during the surgical procedure are arguments for general anesthesia.

11 What are the hallmark features of multiple sclerosis?

The corticospinal tract neurons of the brain and spinal cord show random and multifocal demyelination, which slows nerve conduction, resulting in visual and gait disturbances, limb paresthesias and weaknesses, and urinary incontinence. There is increasing evidence that there is demyelination of peripheral nerves as well. The onset of disease is typically between the ages of 15 and 40 years. The cause appears to be multifactorial, including viral and genetic factors. The course of multiple sclerosis is characterized by symptomatic exacerbations and remissions, although symptoms eventually persist. Female patients often experience remission during pregnancy. Symptoms of multiple sclerosis (MS) usually develop over a few weeks, persist for a few months, and resolve to varying degrees over a few months. The etiology is unknown; however, viral infection leading to immunologically mediated destruction of myelin is one hypothesis.

12 Do steroids have a role in the treatment of multiple sclerosis?

Steroids may shorten the duration and severity of an attack but probably do not influence progression of the disease. Other therapies such as immunosuppressive drugs, interferon, and plasmapheresis are also occasionally of benefit.

13 What factors have been associated with an exacerbation of multiple sclerosis?

Emotional stress, fatigue, infections, hyperthermia, trauma, and surgery may exacerbate symptoms. It is thought that elevated temperature causes complete blocking of conduction in demyelinated neurons.

14 Review some perioperative concerns for patients with multiple sclerosis. Are medications used for most general anesthetics safe?

Surgical stress most likely will exacerbate the symptoms of MS. Even modest increases in body temperature (>1° C) must be avoided. There are no known unique interactions between MS and drugs selected for general anesthesia. However, severe disease is often accompanied by varying degrees of dementia. Demented patients will likely have an increased sensitivity to the sedative effects of anesthetic agents, and short-acting agents are recommended. Controlling the known factors associated with MS exacerbation is more important than the choice of medications for general anesthesia.

15 Are local anesthetics especially toxic for patients with multiple sclerosis?

Above threshold concentrations local anesthetics are neurotoxic. This potential may be amplified in the setting of MS because of the loss of the protective effect of the myelin, resulting in the spinal cord and nerves being exposed to higher local anesthetic concentrations.

16 Are epidural and spinal anesthesias safe for patients with multiple sclerosis?

Regional anesthesia may be beneficial in the patient with MS because of a decreased stress response to surgery. Epidural anesthesia is considered safe by most authorities. The safety of peripheral nerve blocks cannot be guaranteed as evidenced by a patient with MS sustaining a severe brachial plexopathy after intersclane block (see Koff 2008). Exacerbation of MS symptoms has been reported after spinal anesthesia. This difference in outcomes may be caused by reduced concentrations of local anesthetic at the spinal cord when epidural is compared to spinal techniques and there is less exposure of unmyelinated nerve roots to local anesthetics. When performing an epidural anesthetic or labor analgesic, recommendations are to use the minimum dose necessary and to use shorter-acting agents. Supplementation with epidural opioids will also reduce the local anesthetic requirement. In summary, spinal anesthetic is a technique best avoided in patients with MS.

17 Are muscle relaxants safe in patients with multiple sclerosis?

Since these patients (particularly the patients with severe disease) can have significant motor impairment with associated muscle wasting, succinylcholine might be best avoided because of a potential hyperkalemic response. Lower doses of nondepolarizing relaxants should be used in patients with baseline motor weakness. Shorter-duration nondepolarizing relaxants may be advantageous in this situation.

18 Describe postpoliomyelitis syndrome

Postpolio syndrome is characterized by progressive weakness of the previously affected muscles that begins years after a severe attack of poliomyelitis. Muscles never affected by polio are less often affected. Common signs and symptoms include fatigue, cold intolerance, joint deterioration, muscle pain, atrophy, respiratory insufficiency, dysphagia, and sleep apnea. Patients with postpolio syndrome who complain of dysphagia may have some degree of vocal cord paralysis. Some patients have decreased lung function, and considerable cardiorespiratory deconditioning may also be present.

19 What are the anesthetic considerations for patients with postpolio syndrome?

Patients should be informed about the possibility of postoperative mechanical ventilation. If sleep apnea is present, the patient may have coexisting pulmonary hypertension. Dysphagia and vocal cord paralysis may place patients at increased risk for aspiration. If progressive skeletal muscle weakness is present, succinylcholine should be avoided because of the possibility of exaggerated potassium release.

20 Review critical illness polyneuropathy and the patient subsets prone to developing it

As many as 70% of patients with sepsis, multiple organ dysfunction, or systemic inflammatory response syndrome develop generalized weakness associated with sensory loss and other neurologic findings. This syndrome has been termed critical illness polyneuropathy (CIP). The longer the duration of the underlying illness, the more severe the weakness. Patients with mild or moderate underlying critical illness are likely to have improvement in strength once their primary condition improves, although death is not infrequent in those severely affected (and usually related to the primary illness). Although the mechanism is unknown, it is thought to be a disturbance of the microvasculature, resulting in neuronal ischemia and increased capillary permeability. Factors that may be associated with CIP include long-term administration of muscle relaxants, steroids, malnutrition, and hyperglycemia.

21 Describe the clinical features of critical illness polyneuropathy

Failure to wean is the most common presentation, but coexistent encephalopathy often clouds the clinical picture. Severe cases may present as areflexic quadriparesis. Other clinical characteristics include predominantly distal limb weakness with muscle wasting, decreased or absent deep tendon reflexes, and variable sensory loss, often in a stocking and glove distribution. Cranial nerves are intact. Creatine kinase levels are normal or slightly elevated. Cerebrospinal fluid is normal. Biopsies of nerves show fiber loss with axonal degeneration, whereas muscle biopsies demonstrate denervation atrophy. Electrophysiologic studies reveal an axonal polyneuropathy.

22 Review the anesthetic concerns in patients with critical illness polyneuropathy

The response to nondepolarizing relaxants cannot be predicted. Succinylcholine should be avoided out of concerns for hyperkalemia. The associated medical problems are probably the greatest risk for the patient.

Note: Perioperative neuropathies are discussed in Chapter 20.

KEY POINTS: Degenerative Neurologic Diseases image

1. Patients with neuropathies often are aspiration risks secondary to bulbar muscle weakness.
2. Similarly, orthostatic hypotension is a common finding.
3. Often these patients require postoperative mechanical ventilation.
4. Because of denervation atrophy, succinylcholine may produce severe hyperkalemia, resulting in cardiac arrest. Thus succinylcholine should be avoided.
5. The response to nondepolarizing muscle relaxants is unpredictable, but most of these patients are probably sensitive to them.
6. Spinal anesthesia should be avoided in patients with multiple sclerosis.
7. With the exception of spinal anesthesia in multiple sclerosis, neither general nor regional anesthesia exacerbates the course of disease in the neuropathies described.

SUGGESTED READINGS

1. Brambrink A.M., Kirsch J.R. Perioperative care of patients with neuromuscular disease and dysfunction. Anesthesiol Clin. 2007;25:483-509.

2. Koff M.D., Cohen J.A., McIntyre J.J., et al. Severe brachial plexopathy after a ultrasound-guided single-injection nerve block for total shoulder arthroplasty in a patient with multiple sclerosis. Anesthesiology. 2008;108:325-328.

3. Perlas A., Chan V.W. Neuraxial anesthesia and multiple sclerosis. Can J Anaesth. 2005;52:454-458.

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