Sensory Disturbance and Pain

Sensory disturbances are common at presentation and affect several patients with MS at some point during the course of their disease. Patients may experience numbness, tingling, the sensation of pins-and-needles, coldness, and feelings of tightness or swelling in the limbs and trunk.

More than half of all patients experience chronic or acute pain syndromes as either a direct consequence of MS, or indirectly as a consequence of the disability created by the disease process. Pain can be characterized into 4 categories: neuropathic pain, acute pain due to the inflammatory process, pain caused by increased muscle tone, and musculoskeletal pain from poor body posture, improper positioning, or paraplegic shoulder. Patients with MS may experience trigeminal neuralgia, the sensation of electric shock radiating down the spine or into limbs on neck flexion (Lhermitte sign), dysesthetic pain, back pain, visceral pain, and pain secondary to muscle spasms.

Pain is associated with longer disease duration and spinal cord involvement. The older population often reports pain as the most distressing symptom. Aging is associated with musculoskeletal degeneration, which can further aggravate painful conditions. Studies have shown that patients with MS are often under-treated for pain, which can result in increased morbidity.

Medication useful for treating pain in this population includes opioid analgesics, nonsteroidal antiinflammatory drugs (NSAIDS), antiseizure medication, antidepressants, antispasticity agents, and cannibiods. An intrathecal pump may also be beneficial for intractable pain and spasms.

It is important to consider side effects when prescribing medication to the elderly, and dose adjustments may be necessary. Side effects of opioids include constipation, respiratory depression, confusion, and lethargy. Carbamazepine and other anticonvulsants may increase confusion and ataxia in the elderly. Tricyclic antidepressants (TCAS) or other medications with anticholinergic effects may lead to urinary retention, confusion, cardiac symptoms, and autonomic instability. The NSAIDS should be used with caution in the elderly because of the increase risk of hypertension, myocardial infarction, stroke, gastrointestinal bleeding, and renal insufficiency.

The antidepressant duloxetine, which is a selective serotonin and a norepinephrine reuptake inhibitor, is approved for treatment of pain from secondary diabetic neuropathy and fibromyalgia. It has been used off label for other types of neuropathic pain. Studies have shown duloxetine to be safe and effective in the geriatric population although most of these studies involved the use of duloxetine for conditions other than pain. Nausea and headache are the most common side effects, but the drug can also cause orthostatic hypotension and hyponatremia, both of which may affect the aging population more prominently. (Duloxetine for Multiple Sclerosis Pain. http://www.ClinicalTrials.gov ).

Although many pain syndromes are solely caused by MS, pain complaints in an aging population should be evaluated for other possible causes. Cervical and lumbar spondylosis may occur in conjunction with MS. Clues to help identify cases of spondylosis include neck or back pain, radicular pain in the extremities, muscle atrophy in a segmental distribution, and the loss of deep tendon reflexes. MRI of the cervical or lumbar spine should be part of the diagnostic work-up. Surgery may be beneficial for select patients.

Fatigue

Fatigue is present in two-thirds of patients with one half describing fatigue as the most disabling symptom. Common features of MS fatigue include malaise, motor weakness during sustained activity, and difficulty maintaining concentration. An aging patient with MS who complains of fatigue should be evaluated to rule out other potential causes including infection, cancer, anemia, hypothyroidism, rheumatologic disorders, sleep apnea, and diseases of the cardiovascular, pulmonary, renal, or hepatic system. Medications that can contribute to fatigue include TCAS, selective serotonin reuptake inhibitors, benzodiazepines, opioids, anticonvulsants, β-blockers, interferons, and antispasticity medications. Other factors that can lead to fatigue include depression, pain, physical deconditioning, disrupted sleep secondary to neurogenic bladder, and exposure to a heated environment. Once other causes have been ruled out, treatment of fatigue includes energy conservation, exercise program, and medication. Aerobic exercises in particular have been shown to be beneficial in reducing fatigue. Medications include amantadine, modafinil, and methylphenidate. The use of stimulants in the aging population should be used with caution because of the increased risk of cardiac side effects. Methylphenidate has been associated with increased heart rate, but has been shown to be safe and effective in adult populations with traumatic brain injuries. Amantadine has been associated with an increase in risk of confusion and edema in the elderly.

Depression

Depression is the most common mood disorder affecting more than half of patients. The incidence of depression in MS is 3 times higher than in the general population and more common even compared with other chronic disease states. Depression may be overlooked as there are symptoms common to both, such as fatigue, reduced activity, decreased appetite, and poor concentration. MS is associated with a 7.5 times higher suicide rate than in the general population, which cannot be explained fully by a reactive depression. In general, suicide rates increase with age. Risk factors for suicide include major depression, living alone, and alcohol abuse. Duration of MS, severity of physical disability, and cognitive impairment do not affect the risk of suicide. Drugs that can cause depressive symptoms include anxiolytics, β-blockers, methyldopa, clonidine, reserpine, interferon, and steroids. Depression rating scales that are currently used may have limited use in the MS population. The widely used Beck Depression Inventory evaluates depression based on responses to 21 questions, but the questions may overlap with the symptoms of MS itself, such as fatigue. The same is also true for the Geriatric Depression Scale. How common depression scales should be modified to better evaluate the MS patient is still unclear at this time.

Cognitive Dysfunction

Fifty percent of patients with MS suffer from some form of cognitive dysfunction. Changes in cognitive ability can significantly impair the ability to work and live independently. Even though mild cognitive dysfunction occurs frequently, only 5% to 10% of patients will develop a severe cognitive dysfunction. Cognitive deficits involve loss of short-term memory, reasoning, verbal fluency, visuospatial functions, abstract reasoning, and speed of processing information whereas intellectual functions and language skills are generally unaffected. Decreased short-term memory is the most common finding. Patients show slowed retrieval of formed memories and often require cueing. Aging itself causes a slowing in the frontal lobe, which can lead to a slower learning rate and difficulty with memory. Thus, the aging patient with MS may be at an even greater risk for significant cognitive disturbance. Patients should be encouraged to use lists, daily journals, and appointment books for activities. The Mini-mental Examination may be useful in tracking changes in cognition but it may be insensitive to detect subtle cognitive changes occurring in most patients with MS. The patient’s medications should be assessed for possible effects on cognitive function. Medications that can contribute to cognitive slowing, especially in the aging population, include anticholinergics, antispasmodics, opioids, benzodiazepines, and TCAS. Consideration should be given to a change to long-acting anticholinergic preparations for bladder dysfunction. The use of intrathecal medications or botulinum toxin injections may be used to reduce high doses of oral antispasticity agents. As always, it is important to monitor for signs of depression, anxiety, or fatigue, which may exacerbate cognitive difficulties.

Opthomalogical Dysfunction

Disturbances of the visual system are among the most common manifestations of MS, affecting up to 80% of patients at some time during the disease course. These abnormalities can result in significant disability, culminating in an inability to work and compromising the patient’s activities of daily living. The most common visual manifestations of MS are optic neuritis, internuclear ophthalmoplegia, and nystagmus. Symptoms may include blurred vision, scotoma, impaired color vision, and diminished contrast sensitivity. Visual changes are also common in the aging population with the development of cataracts, presybopia, macular degeneration, and glaucoma, which can lead to further social isolation and difficulty in self-care. Useful recommendations may include the outlining of doorways, steps, and wall switches with tape or markers, the use of magnifiers, and glare reduction. Using eyeglasses with prisms, or having the patient patch one eye, may minimize diplopia.

Cerebellar Symptoms

Cerebellar lesions are seen in one-third of patients with MS. Tremor in MS can be one of the more disabling symptoms of the disease and can affect any muscle group. Tremors can increase fatigue by causing an increase in energy consumption. Although there is no effective treatment, medications used include propranolol (Inderal), clonazepam (Klonopin), primidone (Mysoline), and isoniazid (risk of hepatitis increases with age >35 years). Stereotactic surgery is not recommended.

Motor Loss and Spasticity

Corticospinal tract involvement is present in 62% of patients with progressive disease. Spasticity and weakness usually have a greater effect on the lower extremities. The weakness associated with aging is a result of lower motor neuron denervation and muscle atrophy.

The energy requirement for an activity is increased with the presence of spasticity. The aging patient with increased spasticity needs to be evaluated to rule out secondary causes such as infections, skin breakdown, spinal stenosis with myelopathy, or other disease processes. Oral antispasticity medication may be poorly tolerated by the older population and should be monitored closely. Baclofen use in an elderly patient will require an initial lower dose and a slower titration to decrease the risk of sedation and confusion. Tizanidine should also be used with caution in the elderly because clearance of the drug is decreased fourfold. Monitoring for hypotension and sedation is essential. The benzodiazepines are traditionally poorly tolerated in the older population and are associated with an increased half-life and a higher association of paradoxic reactions, agitation, and disequilibrium.

Bladder Disturbance

Ninety-six percent of patients for have had MS for more than 10 years will develop urological symptoms, with detrusor hyperreflexia being the most common. Using oxybutynin or tolterodine for the treatment of detrusor hyperreflexia in clinical studies was found to be safe in older and younger patients. Anatomic and physiologic changes because of aging can cause urinary frequency, incontinence, hesitancy, retention, and nocturia. Incontinence may also be due to delirium, atrophic vaginitis, enlarged prostrate, constipation, and endocrine disorders. Women should be evaluated for estrogen replacement and men should have routine prostate evaluation. The elderly are especially sensitive to the urological side effects of medications. Alpha blocking agents used to treat sphincter dysnergia may cause a higher incidence of orthostasis in the elderly. Urinary tract dysfunction can lead to the formation of bladder and renal stones and frequent urinary tract infections. Urinary retention or frequent catheterization can lead to frequent urinary tract infections, commonly with antibiotic-resistant organisms. Treatment of urological symptoms should take into account the patient’s level of disability, degree of reversibility of symptom, ability to function independently, other medical problems, and social support networks. For instance, before initiating a program of clean intermittent catheterization, a careful assessment of coordination, vision, cognitive function, and manual dexterity needs to be completed. If intermittent catheterization is impractical, a suprapubic or urethral indwelling catheter can be used. Chronic indwelling catheters can lead to colonization of the urinary tract, which may lead to chronically positive urine cultures, even in the absence of infections. Other disadvantages include increased risk of bladder calculi and bladder cancer. In patients with poor mobility, dexterity, or significant lower extremity spasticity, an augmentation cystoplasty with a catheterizable abdominal stoma may facilitate catheterization.

Bowel Disturbance

Constipation as a result of pelvic floor spasticity, decreased gastro-colic reflex, inadequate hydration, medication, immobility, and weak abdominal muscles, is the most common bowel dysfunction. The elderly are also at risk for constipation because of slowed motility of the gastrointestinal tract. Many medications can exacerbate constipation, especially in the elderly. The TCAS or other medications with anticholinergic side effects, antihypertensives (especially the calcium channel blockers), iron, calcium, and opioid agents are common offenders. Fecal incontinence can result from sphincter dysfunction, constipation with rectal overflow, and diminished rectal sensation. A regular bowel program including stool softeners, promotility agents, and timed evacuation may be necessary. Changes in bowel habit need to be investigated to exclude colon cancer, diverticular disease, thyroid disease, or other medical causes.

Sexual Disturbance

Most patients with MS and their partners suffer from some form of sexual dysfunction. Primary sexual dysfunction is due to lesions in the CNS that cause loss of libido, decreased genital sensation, decreased orgasmic response, difficulty in achieving an erection, or decreased vaginal lubrication. Secondary sexual dysfunction occurs due to other symptoms of MS such as bowel and bladder problems, spasticity, and so forth. Tertiary sexual dysfunction is related to psychosocial and cultural issues. Sexual changes that occur commonly in the elderly include impotence, orgasmic dysfunction, and dyspareunia. A sexual history should be taken routinely and treatment options should be discussed with the patient and their partner. Phosphodiesterase 5 inhibitors should be used with caution in the elderly due to possible cardiac side effects.

Heat Intolerance

MS is associated with an increase in severity of symptoms with heat caused by environmental factors, over exertion, or pyrexia. The elderly are vulnerable to hyperthermia due to loss of homeostatic temperature regulation, declining function of the autonomic nervous system, decrease in sweat gland function, and loss of subcutaneous fat. To help manage heat intolerance, outside activities should be timed for early morning, energy conservation techniques should be used, and air conditioning should be used in homes and cars. Cooling vests and light-colored clothes may be useful, saunas and hot tubs should be avoided, and pool temperatures should be less than 30°C (86°F).

Swallowing Difficulties

Swallowing disorders have been estimated to affect 3% to 20% of patients with MS. Oral intake and nutritional status should be closely monitored in these patients. Swallowing studies may be needed for evaluation and patients with severe dysphagia may require enterostomal feedings. Elderly patients may develop deficits, such as ineffective pharyngeal peristalsis and reduced motility of the esophagus leading to reflux, achalasia, and hiatal hernia, and this can exacerbate the dysphagia associated with MS.

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