A 76-Year-Old Man With Subacute Onset of Leg Weakness
Author:
Ronald N. Rubin, MD—Series Editor
Citation:
Rubin RN. A 76-year-old man with subacute onset of leg weakness. Consultant. 2019;59(5):149-151.
A 76-year-old man presents with weakness of the legs of subacute duration. A careful history plots the onset at 1 to 2 years ago—he reports that a daily walk with friends on a walking path near his home had become increasingly more difficult to the point that he is no longer able to do it. Also, he reports that when he travels on an airplane, he now requires either wheelchair or golf cart assistance to navigate the airport. His sole symptom has been weakness, always symmetric, and never with accompanying pain of any kind. He reports that the weakness comes on as he ambulates, currently within half a block of initiating the walk. When he stops and rests, the weakness abates such that he can resume walking—but again, the weakness returns, often after having walked a lesser distance.
He has a many-years history of bilateral lower-extremity sensory neuropathy in a stocking distribution, which manifests as tingling, more prominently at night, and which he assumes to be related to his type 2 diabetes mellitus. The diabetes has been present for 25 years, and the neuropathy symptoms for 10 years. He has no other neurological symptoms.
His medical history is positive for the aforementioned type 2 diabetes mellitus, which has been managed with a variety of oral agents. He has mild hypertension that has been well controlled with an angiotensin-converting enzyme inhibitor. He had had poliomyelitis at age 11 affecting his legs but had made a good recovery to the point of being a star athlete in multiple sports in high school.
Physical examination findings include a blood pressure of 120/84 mm Hg, a pulse of 72 beats/min, a respiratory rate of 12 breaths/min, a temperature of 37°C, and a body mass index of 31 kg/m2. Examination of the head, eyes, ears, nose, and throat reveals normal findings, including intact cranial nerve function and visual fields. The chest is clear to auscultation, and the heart has regular rate and rhythm without murmurs or gallops. There are no carotid bruits. Neurological examination reveals normal strength, sensation, and reflexes in the upper extremities. There are no tremors or rigidity. The lower extremities have normal tone and muscle bulk without fasciculations. Ankle reflexes are absent bilaterally. Pinprick and vibration sensation are absent bilaterally below the knees. The Babinski reflex is absent bilaterally.
Results of a complete blood cell count and a basic and comprehensive metabolic panel are within normal limits, with the exception of an elevated glucose level of 140 mg/dL and an elevated hemoglobin A1c of 6.2%. A computed tomography study of his lumbosacral spine shows disk degeneration at L4-5 and L5-S1 but no central canal stenosis or foraminal encroachment at any level.
Answer: C, postpolio syndrome
The case presented here is an example of postpolio syndrome. This is a condition with little in the current general literature but that was well described in the 1980s and 1990s, reflecting the time lag between the last polio epidemics in the United States (in the 1940s and 1950s) and the development of the syndrome. The best data seem to indicate that symptoms appeared in 28.5% to 64% of patients who had had paralytic poliomyelitis (with the true incidence perhaps being as high as 80%!), with the usual time lag of approximately 35 years from acute infection (again with considerable variation).1,2
Risk factors and demographics for postpolio syndrome include severity of initial paralysis, age at initial infection (polio is generally worse in adolescents and adults), and the amount of physical activity during intervening years.2 Interestingly, our patient had had polio at age 11 and had participated in very high-level sports for the next decade and a half thereafter.
The presentation and clinical manifestations of postpolio syndrome are dominated by weakness and fatigue in the affected muscles with any exertion. The weakness usually abates with rest, allowing resumption of, for example, walking, but the symptoms return shortly after doing so. The patient will often have as chief complaint the decreased mobility in daily life along with severe fatigue generally, and not just in affected muscles. Our patient’s presentation was quite classic in this regard.
There are no definitive studies or blood tests for this diagnosis. Rather, it remains a diagnosis of exclusion with the following criteria: (1) a confirmed past episode of poliomyelitis with residual motor neuron loss; (2) recovery and stability for a period of more than 15 years; (3) gradual (most common) or acute (uncommon) onset of new weakness or fatigue in affected muscles; and (4) exclusion of other conditions that can cause similar symptomology.2 Again, our patient’s case fulfills these criteria.
The pathogenesis is conjectural rather than definitively defined. Virology and immunology studies have excluded recurrence of polio or persistence of poliovirus. The most accepted theory is that of “neuron overload,” whereby the remaining neurons (each with its motor unit muscle fibers) attempt to compensate and sprout new nerve terminals to “orphaned “ muscle fibers whose neuron had been killed by the poliovirus. In time, this additional strain adversely effects the neuron, with loss of the new axons and even loss of the neuron itself with the resultant symptomology.1-3 This is not unlike chronic pressure overload (aortic stenosis) or volume overload (aortic regurgitation) or tachycardia resulting in cardiac muscle dysfunction and congestive heart failure, even though the cardiac tissue itself started out as totally normal.
Prognostically, the syndrome usually stabilizes or very slowly progresses (1%-2% loss in muscle strength per year). Fatality is uncommon except in the event of severe bulbar presentations that can result in swallowing and/or respiratory dysfunctions. Physical medicine and rehabilitation for strength and endurance are necessary but require expertise in the management of postpolio syndrome, because training to the point of fatigue is actually counterprotective—an outstanding example of the fallacy and toxicity of the “no pain, no gain” mantra too frequently employed. Lifestyle changes such as single-floor living, energy conservation, reduced workload, and daytime sleeping usually can result in retention of adequate functional status.
Parkinson disease (Answer A) often affects the similar age demographic and can mimic the symptoms of postpolio syndrome. A professional neurological examination will usually demonstrate the history or physical presence of resting tremor somewhere, and muscle rigidity more generally, neither of which were present in our patient’s case. Myasthenia gravis (Answer B) affects small muscles (eg, the eyelids) rather than the larger muscle groups such as those of the lower extremities. Myasthenia gravis also is characterized by marked weakness and fatigability of muscles, but with a special affinity for muscles innervated by the bulbar nuclei such as those of the face, eyes, tongue, and throat, leading to ptosis, diplopia, and speech difficulties. It most commonly occurs in younger women, not the demographic of the patient in our case. Thus, myasthenia gravis is a poor fit in our patient and not the most likely diagnosis here.
Diabetic neuropathy (Answer D) is very likely present in the presented patient and is itself a diagnosis of exclusion. However, the typical findings are sensory deficits more than motor deficits. Mononeuritis multiplex can affect both but will essentially always be focal and nonsymmetric as indicated by its very name. Most commonly there is a stocking distribution of sensory nerve loss, relatively symmetrically below the knee and in the feet. Muscle weakness as either a symptom or a physical finding would not be expected, such that it is not the most likely explanation here.
PATIENT FOLLOW-UP
A nerve conduction study and electromyography revealed a length-dependent sensorimotor polyneuropathy, axonal type, consistent with diabetic neuropathy. Motor units were decreased in number and recruitment in all muscles tested in the legs. Additionally, chronic changes were noted in all muscles tested below the knees, likely reflecting a history of polio. He will seek dietitian-aided weight loss to ease the burden on his legs. He was referred to a physical medicine and rehabilitation specialist with expertise in postpolio syndrome rehabilitation and lifestyle adjustments.
Ronald N. Rubin, MD, is a professor of medicine at the Lewis Katz School of Medicine at Temple University and is chief of clinical hematology in the Department of Medicine at Temple University Hospital in Philadelphia, Pennsylvania.
TAKE-HOME MESSAGE
Postpolio syndrome is an uncommonly seen reappearance of symptoms (muscle weakness) decades after the acute event. It is uncommon, given the fact that since 1955, polio has been extremely rare in the United States, and the fact that the age of the population of such patients now exceeds 65 years, such that the potential pool of patients has shrunken considerably due to age-related mortality. However, of 100 such polio cases living that long, the incidence of developing postpolio syndrome is quite high, perhaps in the 50% range. The diagnosis thus needs be included in any patients with new weakness who have a remote history of poliomyelitis.
References:
- Dalakas MC, Elder G, Hallett M, et al. A long-term follow-up study of patients with post-poliomyelitis neuromuscular symptoms. N Engl J Med. 1986;314(15):959-963.
- Jubelt B, Agre JC. Characteristics and management of postpolio syndrome. JAMA. 2000;284(4):412-414.
- Pascuzzi RM. Poliomyelitis and the postpolio syndrome. Semin Neurol. 1992;12(3):193-199.