doi: 10.2169/internalmedicine.7985-21
Intern Med Advance Publication
http://internmed.jp【 CASE REPORT 】

Postpolio Syndrome from Non-Paralytic Poliovirus Infection
Kengo Maeda and Yoshiko Sugihara

Abstract:
A 73-year-old man presented with muscle weakness and atrophy of his right arm. Atrophy of his left brachia and left calf had occurred 13 years before without any improvement or deterioration. His sister andcousin had a history of paralytic poliomyelitis. Serum poliovirus type 2 neutralizing antibody was elevated to128x. Electromyography revealed chronic denervation potentials not only in the muscles affected previously
but also in the unaffected muscles. Acute and chronic denervation potentials were found in the newly affectedmuscle. Postpolio syndrome should be considered in patients with unilateral muscular atrophy even when
they have no history of paralytic poliomyelitis.
Key words: postpolio syndrome, non-paralytic poliomyelitis, electromyography(Intern Med Advance Publication)(DOI: 10.2169/internalmedicine.7985-21)

complaining of persistent weakness of these muscles. Theweakness had been unchanged without additional weakness
for nine years. He had a family history of paralytic poliomyelitis in his sister and cousin in their childhood. He had
never been abroad. No facial or bulbar palsy was found. Hisleft deltoid, biceps and triceps brachii, and calf muscles
were weak and atrophic (Fig. 1). No fasciculation was observed in those muscles. He did not show any sensory disturbances. Neither deep tendon reflexes nor pathological reflexes were elicited. A nerve conduction study (NCS) wasnormal. Serum neutralizing antibodies for poliovirus types 1,2, and 3 were <4, 128x, and <4, respectively. He was thus
diagnosed with PPS.
We simply advised him not to exercise too much. He
stopped coming to our hospital until he recognized weakness of the right arm four years later. The level of serum
creatine kinase was slightly elevated to 317 IU/L. An NCS
including the bilateral median, ulnar, radial, tibial, peroneal,and sural nerves did not show any evidence of demyelination. No findings of pleocytosis, increased protein or IgG index values, or oligoclonal IgG band were detected in theCSF, nor were any neutralizing antibodies for poliovirus.
MRI of the cervical cord revealed mild spondylosis with canal stenosis. There was no lesion in the spinal cord (Fig. 2).
EMG findings were characteristic (Table).
The muscles affected previously (left deltoid and left anterior tibial) showed chronic denervation potentials, such as

Introduction
The term “postpolio syndrome (PPS)” is applied to paralytic poliomyelitis survivors who develop new weakness or
fatigue after achieving a long-term stable condition (1). The
new weakness and atrophy affect both previously affectedand unaffected muscles. Typically, these are asymmetrical orsegmental (2). Polioviruses damage spinal motor neurons in
the anterior horn. When the damage is less severe, paralysis
is not recognized. An electromyographic (EMG) study revealed that unaffected muscles of PPS patients have large
motor units as a result of effective reinnervation (3). Thereis a possibility that PPS may occur in people with nonparalytic polio.

Case Report
Our patient was a 73-year-old Japanese man who, at 60years old, had noticed weakness and atrophy of his left armand calf. At that time, a blood test, including evaluations ofanti-Jo-1 antibody, anti-nuclear antibody, anti-acetylcholine
receptor antibody angiotensin converting enzyme, lactate/pyruvate, vitamin B1 and B12, anti-scl-70 antibody, and thyroid hormones, a cerebrospinal fluid (CSF) examination, andmagnetic resonance imaging (MRI) of the whole spinal cord
were all normal. At 69 years old, he came to our hospital

Department of Neurology, National Hospital Organization Higashi-Ohmi General Medical Center, Japan
Received: May 17, 2021; Accepted: January 14, 2022; Advance Publication by J-STAGE: March 5, 2022
Correspondence to Dr. Kengo Maeda, maeda@vories.or.jp

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DOI: 10.2169/internalmedicine.7985-21

Figure 1. Photographs of the patient at the first visit. Muscular atrophy of the left arm (A) and calf(B) is prominentings, we diagnosed him with PPS from non-paralytic polio
infection.
However, a careful differential diagnosis is necessary incases with asymmetrical and/or segmental weakness withmuscular atrophy. First, amyotrophic lateral sclerosis (ALS)
was excluded based on the fact that the patient’s symptoms
of weakness and muscular atrophy of his left arm and calf
had not progressed for more than 10 years and that somemuscles with a normal strength showed chronic denervation
potentials without acute denervation potentials. Furthermore,
the patient had no symptoms or signs of upper motor neurons. He also did not develop bulbar palsy or respiratory
failure. Second, cervical spondylotic amyotrophy known as
Keegan’s cervical spondylosis should be excluded. This disease affects limited muscles innervated by the locally compressed anterior roots. Widespread abnormalities on an EMG
do not indicate this disorder. However, the presence of cervical canal stenosis may influence the patient’s symptoms.
Motor systems that were pre-injured by a polio infection
and decreased in the number of motor neurons might besusceptible to the compression whose power is not strong
enough to cause muscle weakness and muscular atrophy innormal condition. Third, multifocal motor neuropathy(MMN) should be excluded. MMN is an immune-mediateddemyelinating neuropathy. NCSs including the bilateral median, ulnar, radial, tibial, peroneal, and sural nerves excluded
demyelinating neuropathy in the present case based on theabsence of decreased nerve conduction velocity or conduction block. Fourth, poliomyelitis itself, not PPS, should beconsidered. Our patient had never traveled abroad. In Japan,
a live vaccine was used for polio vaccination (OPV) until
2012. The OPV is a cause of vaccine-induced poliomyelitis;
however, our patient did not receive the OPV. His grandsons
had received the OPV one- year before the onset of this patient, but our patient did not have a fever, or other infectious
symptoms at that time, and the interval of one- year seems
be too long for this to have been a case of vaccine-induced
poliomyelitis. Fifth, Hirayama disease affects young people,
and the onset age differs markedly from this patient. Al-Figure 2. Sagittal view of the cervical spinal cord on T2weighted MRI.

single oscillation of giant motor unit action potentials without acute denervation potentials. The right biceps brachii
muscle, newly affected, showed both acute and chronic denervation potentials. The unaffected muscles (left extensor
digitorum communis, left iliopsoas, and right iliopsoas)
showed chronic denervation potentials with effective compensation. The unaffected right anterior tibial muscle
showed acute and chronic denervation potentials, suggestingthat weakness of this muscle might be ongoing.

Discussion
Our patient had a family history of paralytic poliomyelitis
affecting his sister and cousin. He has never received theoral poliovirus vaccine (OPV), nor had he ever been topolio-endemic areas. He did not suffer from acute paralytic
poliomyelitis. The presence of neutralizing antibody against
type 2 poliovirus suggested that he might have been infected, possibly due to close contact with his sister. Basedon the clinical features, serological evidence, and EMG find2

Intern Med Advance Publication

DOI: 10.2169/internalmedicine.7985-21

Table. Results of Electromyography.
Muscles

Resting

Weak contraction

Interference

Previously affected
L deltoid
L anterior tibialis

F (-), P (-)
F (-), P (-)

giant, 8mV
giant, 9mV

poor
poor

Newly affected
R biceps brachii

F (-), P (+)

giant, 9mV

poor

Unaffected
L extensor digitorum communis
L iliopsoas
R extensor digitorum communis
R iliopsoas
R anterior tibialis

F (-), P (-)
F (-), P (-)
F (-), P (-)
F (-), P (-)
F (+), P (-)

giant, 12mV
giant, 7mV
normalgiant, 12mVgiant, 8mV

normalfair
normalpoor
fair

L: left, R: right, F: fibrillation potential, P: positive wave

though the serum level of CK was increased slightly, muscle
diseases, such as myositis and muscular dystrophy, were denied by the EMG findings. Hypothyroidism had been excluded at the previous hospital. Mononeuropathy multiplex
induced by vasculitis was not suggested due to the patient’ssymptom (no sensory symptoms), NCS findings, and blood
test results.
The present patient showed a stepwise deterioration. We
therefore believe that our patient experienced a deteriorationof his symptoms at least three times. When we saw him forthe first time (at 69 years old), his left arm and left calf had
been already affected. We do not believe that they were affected at the same time. One study followed 52 patients who
had previously had poliomyelitis for 4 years. That study detected only small changes in the muscle strength and disability (4). However, some case studies have observed deterioration in different motor innervation segments in
PPS (5, 6).
A total of 95% percent of polio-infected patients develop
non-paralytic disease, presenting with a flu-like illness; however, in 5% of cases, paralytic polio develops (7). The diagnostic criteria for PPS are 1) prior paralytic poliomyelitis; 2)a period of partial or complete functional recovery after
acute poliomyelitis, followed by an interval of stable neurological function; 3) the gradual or sudden onset of progressive and persistent new muscle weakness or abnormal fatigability; 4) symptoms persisting for at least one year; and 5)
the exclusion of other neurological, medical, and orthopedic
problems (8). Our patient did not meet these criteria since
he did not have paralytic poliomyelitis. However, PPS-likeweakness or fatigue has been observed in patients with nonparalytic polio (9-13). In a twin- study, 71% of paralytic poliomyelitis patients developed PPS, whereas only 41% ofother twins of non-paralytic poliomyelitis patients developed
PPS (10). Halstead et al. reported that patients with a typicalclinical course, physical findings, and electrophysiologicalfindings without paralytic poliomyelitis should be includedin PPS (12). Motor neuron damage in unaffected muscles
has been reportedly observed both electrophysiologically (3)and pathologically (14-16). PPS should be considered in pa-tients presenting with segmental muscle weakness or atrophy
with an inactive interval.
The authors state that they have no Conflict of Interest (COI).

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