Diaphragm Dysfunction Due to Remote Poliomyelitis in a Patient With Unexplained Dyspnea

Late onset of new neuromuscular symptoms occurring many years after the initial illness is the hallmark of postpolio syndrome (PPS) [1]. In PPS, the new onset of motor weakness usually involves muscles that were previously affected; however, new symptoms also may occur in muscles that were clinically asymptomatic. This new weakness is thought to be due in part to overuse and excessive metabolic stress on the remaining motor neurons, eventually leading to their deterioration [1]. Respiratory compromise as a late feature of PPS has been reported and typically is associated with the following risk factors: history of ventilator assistance during the onset of poliomyelitis, central causes of hypoventilation, cranial nerve involvement, and/or musculoskeletal deformities [1-3]. Although respiratory involvement is seen in only a small minority of patients with PPS, it poses a potentially life-threatening complication that presents a challenge to those who manage it. We describe a patient with a history of remote poliomyelitis with no initial respiratory involvement who was evaluated at our clinic; he had a 3-year history of exertional dyspnea and an elevated left hemidiaphragm revealed on a chest radiograph. A 63-year-old man who had exertional dyspnea for the past 3 years came to our clinic for evaluation. Medical history was pertinent for paralytic polio at age 5 years with weakness involving both legs and possibly his neck and arms. He did not require mechanical ventilation, nor did he experience. By the age of 6 years he was able to walk without the use of adaptive equipment. As an adult he was physically active in several sports and had no functional limitations. Three years before his evaluation in our clinic, the patient experienced new weakness and atrophy in both legs, difficulty walking long distances, and generalized fatigue. At the same time he noted insidious, progressive dyspnea while swimming laps and, more recently, shortness of breath after engaging in routine activities. He denied having any recent injury, illness, weight change, or psychosocial stress. He had no history of any pulmonary illness or repeated respiratory infections and no history of polio-related surgery. A review of systems revealed a remote 12 pack-year smoking history, benign prostatic hyperplasia, nocturia, morning headaches, daytime fatigue requiring afternoon naps, and osteoarthritis of the hands and feet. He denied having hypersomnolence or difficulty with memory, concentration, or attention. On physical examination, the patient appeared to be well developed, well nourished, and in no acute distress. His oxygen saturation on room air was 94%. He did not demonstrate dyspnea at rest, nor was he observed coughing. No flaring of the nares or sinus tenderness was noted. A neck examination revealed no thyromegaly, cervical adenopathy, or jugular venous distention. A chest examination revealed no increased activity of the accessory muscles of respiration. Absence of motion of the left diaphragm was appreciated by percussion. Auscultation revealed dullness and diminished breath sounds at the left base. A musculoskeletal examination revealed mild atrophy of both thighs and no atrophy in the upper limbs or neck. He had no abnormalities of the spine. A neurologic examination revealed no deficit on mental status testing, and the cranial nerves were intact. Sensation and deep tendon reflexes were normal. Manual motor testing was normal except for 4 out of 5 strength in both hip flexors and 4 out of 5 strength in both hip extensors. Spontaneous gait was normal except for mild clawing of the left toes. Cerebellar testing revealed no ataxia. Laboratory tests that included a complete blood cell count, comprehensive metabolic panel, and thyroid function tests were unremarkable, but a chest radiograph showed elevation of the left hemidiaphragm. Pulmonary function tests revealed mild restrictive changes with a forced vital capacity of 3.80 L (77% of predicted), forced expiratory volume in one second of 2.81 L (71% of predicted), forced expiratory volume in one second/forced vital capacity of 0.74, total lung capacity of 5.92 L (81% of predicted), and diffusing capacity of 19.5 mL/min/mm Hg (79% of predicted). Oxygen saturation was 94% on room air. A diaphragm ultrasound evaluation demonstrated paralysis of the left hemidiaphragm, evidenced by no movement during the sniff and cough test, with normal movement observed in the right hemidiaphragm. A computed tomography scan of the chest was unremarkable except for the left hemidiaphragm elevation. Magnetic resonance imaging of the cervical spine revealed mild spondylosis from C5-T1, mild right neuroforaminal narrowing at C6-C7, and moderate left neuroforaminal narrowing from C6-T1. No significant central stenosis was present, and the cervical cord demonstrated normal signals and morphology. Polysomnographic studies revealed moderate to severe snoring and significant sleep-disordered breathing (SDB), with recurrent arousals and sleep fragmentation. The overall respiratory disturbance index was 20 events per hour of sleep, consistent with moderate obstructive sleep apnea (OSA). Severe oxygen desaturation associated with SDB was found. The average oxygen desaturation rate was 89%, reaching a low of 70%. Nonapneic oxygen desaturation may still have been occurring. No significant arrhythmias were noted. Sleep efficiency was reduced at 57%. Sleep architecture was abnormal. Periods of deep sleep and rapid eye movement were reduced. An electrodiagnostic study of the neck revealed rare positive sharp waves and fibrillation potentials in the right C6-C7 cervical paraspinals. The sensory and motor nerve conduction studies (NCS) in both upper limbs demonstrated findings within their respective normative ranges. Phrenic NCS of the hemidiaphragms were performed as described by MacClean and Mattioni [4] as follows: the recording electrode is placed over the xiphoid, the ground electrode is placed over the sternum, and the reference electrode is placed over the eighth rib at the costochondral junction. Stimulation of the phrenic nerve involves placement of the stimulator at the posterolateral border of the sternocleidomastoid (clavicular head) immediately superior to the clavicle, with the patient relaxed and the head and neck in the neutral position. Using the XLTEK Neuromax 1002 electromyograph (Excel-Tech Ltd, Oakville, Ontario, Canada), the phrenic NCS (Figure 1) showed compound muscle action potential latency of 9.2 ms on the right and 9.6 ms on the left (normal: 7.44 ± 0.59 ms). Compound muscle action potential amplitude was 617 μV on the right compared with 147 μV on the left (normal: 845 ± 405 μV). Needle electromyography (EMG) of the hemidiaphragms was performed as described by Bolton [5] with monopolar needle insertion at the eighth intercostal space, at the midpoint between the midclavicular line and the midaxillary line. Needle EMG (Figure 2) of the hemidiaphragms showed enlarged motor unit action potentials, which were more marked on the right than the left, and prolonged durations on the left only (normal duration: <13 ms). Recruitment was markedly reduced, with the left worse than the right. In addition, 0-1+ fibrillation potentials and positive sharp waves were noted in the hemidiaphragm bilaterally. Hemidiaphragm action potentials obtained by stimulating the phrenic nerves at the supraclavicular fossa (500 μV/div, 5 ms/div). The right phrenic motor nerve conduction study demonstrated a borderline prolonged latency value (9.2 ms), with an evoked motor response amplitude in the low normal range (617 μV). The left phrenic motor nerve conduction study demonstrated a mildly prolonged latency value (9.6 ms), with at least a moderate to severe reduction in the evoked motor response amplitude (147 μV). Free-run EMG tracings of the right and left hemidiaphragms (500 μV/div, 10 ms/div).The motor unit action potentials are characterized by significantly enlarged amplitudes on the right (0.6-4.4 mV) and prolonged duration on the left (8-18 ms). The motor unit action potential recruitment patterns were moderately to severely reduced on the right and severely reduced on the left. At an 11-month follow-up appointment in our clinic, the patient reported slow progression of his symptoms of motor weakness. In the interim, he underwent nightly bilevel positive airway pressure (BiPAP) ventilation for his diagnosis of OSA. He experienced marked improvement of his sleep quality, resolution of morning headaches, and modest improvement in generalized fatigue, although he continued to take afternoon naps. His dyspnea upon exertion, however, was essentially unchanged since his evaluation 11 months earlier. A repeat chest radiograph showed no appreciable change compared with the previous study. Follow-up pulmonary function test results were unchanged from those of studies performed at baseline. We present a patient with classic symptoms of PPS involving new weakness and atrophy in both legs. At the same time, in the absence of remote pulmonary compromise, he experienced new respiratory difficulties from unexpected postpolio involvement of both hemidiaphragms. The left hemidiaphragm became nonfunctional sometime before presentation and the right hemidiaphragm showed EMG evidence of acute and chronic denervation compatible with neurogenic compromise. These findings strongly suggest that his presenting symptom of exertional dyspnea was most likely caused by 2 factors: (1) complete loss of left hemidiaphragm function of unknown duration and (2) slow, progressive deterioration of the motor units controlling the function of the right hemidiaphragm. The patient's other complaints of generalized fatigue, morning headaches, and poor sleep quality may have been due to both his diaphragm impairment and his recently established diagnosis of OSA. SDB, primarily the obstructive type, was reported by Hsu and Staats [6] to occur as a late sequelae of polio in a retrospective study of 35 patients with polio who had features of sleep disturbance. SDB is considered an important treatable cause of generalized fatigue and daytime sleepiness [6, 7], usually with dramatic improvement after noninvasive positive-pressure ventilation such as BiPAP. In the study by Hsu and Staats [6], upon follow-up all patients reported improvement in their symptoms with nighttime ventilatory assistance. Our patient did, in fact, have improvement in his level of fatigue and daytime sleepiness after receiving ventilatory assistance with BiPAP. However, no improvement occurred in his exertional dyspnea, which is not a feature of OSA in subjects without neuromuscular disease [8-10]. Nocturia was best explained by the patient's history of benign prostatic hyperplasia. Extensive workup for other causes of his respiratory dysfunction, including peripheral neuropathy or radiculopathy, a tumor, metabolic abnormality, or cervical spinal cord disease, failed to yield positive findings. In addition, there was no indication based on the clinical history or physical examination to suggest a separate neurologic disorder, as was the case in a report by Terao and colleagues [11] in which a patient with an established diagnosis of PPS then presented with advanced respiratory failure due to amyotrophic lateral sclerosis. Histopathologic findings in that case demonstrated Bunina bodies in the motor neurons, a finding consistent with amyotrophic lateral sclerosis. Diaphragm dysfunction has only rarely been described as a feature of PPS. A case report by Imai and Matsumoto [12] details a 49-year-old woman who presented with new onset of left upper limb weakness. Her history included paralytic poliomyelitis affecting all 4 limbs at age 5 years. Phrenic nerve stimulation at the supraclavicular fossa showed marked depression of the left hemidiaphragmatic action potentials with no latency shift and normal right hemidiaphragmatic action potentials. The same study performed 3 years earlier showed normal amplitude values, which suggests that the new changes in the left hemidiaphragm were likely due to progressive involvement of the left phrenic motor neurons from PPS. Reports of unilateral diaphragm paralysis of unknown etiologies have yielded findings on electrodiagnostic study that are similar to our case findings. A study by Lagueny and colleagues [13] describes electrodiagnostic study results in 4 patients with idiopathic unilateral diaphragmatic paralysis. NCS showed reduced compound muscle action potential after phrenic nerve stimulation, and EMG revealed a reduced recruitment pattern. It was notable that neurogenic patterns were detected in the contralateral, normally moving hemidiaphragm of 3 subjects, with limb involvement of all 4 patients. Limited experience is available on the management of patients with PPS who have diaphragm dysfunction and unilateral hemidiaphragm paralysis as a cause of exertional dyspnea. Recommendations are based on the same strategies used to prevent muscle overuse in patients with PPS who do not have diaphragm dysfunction. These strategies include energy conservation, nonfatiguing exercise, and weight loss. Treatment of concomitant conditions such as SDB may improve symptoms such as fatigue, daytime sleepiness, and morning headaches. It is important to monitor pulmonary function after treatment of coexisting conditions. A study by Soliman and colleagues [14] suggests the use of sniff nasal inspiratory pressure to assess and monitor inspiratory muscle weakness because of its increased sensitivity in patients with PPS compared with other noninvasive tests, such as maximum inspiratory pressure and maximum expiratory pressure. Prognosis is unclear in patients with PPS-related unilateral hemidiaphragm paralysis; however, evidence exists that unilateral hemidiaphragm paralysis as a sole clinical entity may have a good outcome. In a recent study of 36 patients with unilateral hemidiaphragm paralysis, Elefteriades and colleagues [15] found 13 cases resulting from iatrogenic (surgical) causes, 7 resulting from a tumor, 6 that were idiopathic, 5 occurring as a result of trauma, and 5 due to viral infection (3 due to poliomyelitis). The majority of these patients presented with dyspnea on exertion, and the authors concluded that survival was excellent based on lengthy follow-up. Dyspnea on exertion in a patient with a history of polio may be due to diaphragm dysfunction. In addition to a routine pulmonary workup, phrenic NCS and hemidiaphragm EMG should be considered in the evaluation of patients with PPS who have respiratory complaints to determine possible inspiratory muscle involvement. Daytime sleepiness and fatigue may be a result of SDB and should be evaluated with a sleep study.

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