2021 年 28 巻 3 号 p. 35-38
Introduction: The cardinal symptom of herpes zoster (HZ) is pain. However, in rare cases, it may be accompanied by motor paralysis. Avoidance of movement due to pain delays the detection of paralysis and can be difficult to differentiate from disuse and side effects of drugs even after pain relief. We report a case in which the diagnosis of unilateral paralysis on manual muscle testing (MMT) led us to conclude HZ paralysis was more likely rather than disuse or drug side effects. Case Report: A 90-year-old man who presented with rash and stinging pain in his right thigh was diagnosed with HZ. Because he was unable to move his right leg due to pain at onset, pregabalin was prescribed. Although pain was alleviated after 3 weeks, he failed to walk. MMT revealed decreased motor function of the right hip and knee joints, so he was diagnosed with paralysis of the right L2 to L4 due to HZ. Discussion: In cases of suspected paralysis due to HZ, detailed examinations should be conducted for differentiation with other pathologies causing muscle weakness.
Herpes zoster (HZ) affects 10％–20％ population at some point in life1). In 1965, Hope Simpson reported that latently infected varicella-zoster virus (VZV) is responsible for HZ2). Motor paralysis due to HZ was first reported by Broadbent in 18663). Akiyama reported that 12 of 1,432 patients clinically presented with motor paralysis4). Thomas and Howard reported that 61 of 1,210 HZ patients presented with muscle weakness5).
Muscle atrophy due to disuse from prolonged lying down and dizziness and weakness caused by medication for neuralgia can cause symptoms similar to motor paralysis, but they are bilateral. Here, we report a case in which the diagnosis of unilateral paralysis on manual muscle testing (MMT) led us to conclude that motor paralysis due to thigh HZ was more likely rather than disuse or drug side effects6). We had obtained the consent to publish from the patient.
The patient was a 90-year-old man (175 cm; 55.7 kg). He was taking insulin for diabetes mellitus, his glycemic control was favorable, and he showed no apparent peripheral neuropathy. Although he had a history of lumbar compression fracture, no neurological symptoms or back pain was noted, he was able to walk without assistance and perform activities of daily living properly.
Rash and stinging pain appeared on the anterior region of the right thigh, and the patient was diagnosed with HZ by a dermatologist at a local hospital. Celecoxib (200 mg/day) and pregabalin (150 mg/day) were prescribed for pain. Hematologic examination at the previous hospital revealed an increase in VZV IgG antibody titer to 23.1 (reference value, less than 0.8). Immediately after the onset, he was unable to move his right leg because of intense pain. Although pain was alleviated after 3 weeks, he failed to walk because of weakness in the lower extremities. So he was referred to our department at 7 weeks after the onset.
The chief complaints upon admission were numbness and lack of right knee muscle strength. On the anterior region of the right thigh, the presence of rash scars approximately 10 cm×15 cm in size with pigmentation was observed (Figure 1). When the muscles surrounding the right knee were flexed, there was pain with numbness localized to the upper medial side of the knee (Figure 1). Using a numerical rating scale, pain was 0 at rest and 5 during movement. However, during passive movement of the lower extremities, pain was not evoked and allodynia was not observed. Sensory decline was noted in a wide area on the anterior L2 region of the right thigh (Figure 1). Muscular atrophy of the lower extremities was not obvious. The muscle strength of the lower back was evaluated as normal because the patient could maintain a sitting position. Muscle strength was evaluated using the MMT and graded by recording numerical scores ranging from 0 to 5, where 0, no activity; 1, trace activity; 2, poor; 3, fair; 4, good; and 5, normal. Six-grade MMT scale of the lower extremities demonstrated that right hip abduction and adduction, external and internal rotation were 2/5, hip joint flexion was 2/5 and extension was 3/5, and knee flexion was 4/5 and extension was 3/5, Plantar flexion and varus/valgus of the right leg and movement of the left lower extremity and upper extremities were normal (Figure 2 and 3). Decreased MMT was limited to the movement mainly involved in the muscle groups controlled by the nerves derived from right L2 to L4; therefore it was inferred that motor neuropathy due to HZ in the same site was the main cause of paralysis. Pregabalin was discontinued on the same day to eliminate the possibility of lower limb weakness caused by the drug. Then there was no improvement in lower extremity movement and no exacerbation of pain. The patient complained of numbing pain at the beginning of movement, but did not mind the pain as he continued to move. So active rehabilitation was initiated immediately, and movement of the knee joint gradually improved. He could walk with a cane after 1 week and with no cane after 1 month.
Skin rash scars and sites of pain
On the anterior region of the right thigh, rash scars with pigmentation approximately 10 cm×15 cm in size after sloughing off of the scabs were observed; pain around the right knee was also noted. Sites of sensory decline. Sensory decline was noted in a wide area on the anterior region of the right thigh.
Manual muscle testing (MMT)
Evaluation of the joint movement of the lower extremities; flexion/extension of the right hip joint, knee joint, and ankle joint.
● Large bullet points show muscles involved with nerves originating from L2 to L4.
・ Small bullet points show muscles innervated by nerves other than those with L2–L4 origin.
Manual muscle testing (MMT)
Evaluation of the joint movement of the lower extremities, abduction, and external and internal rotation of the right hip joint.
●Large bullet points show muscles involved with nerves originating from L2 to L4.
・ Small bullet points show muscles innervated by nerves other than those with L2–L4 origin.
In our case, the affected limb could not be moved because of pain, and it was not possible to confirm the paralysis immediately after the onset. If the elderly wouldn't move for three weeks, disuse could well occur. Most analgesics for neuropathic pain cause dizziness. In many cases, paralysis, disuse and side effects of drugs occur simultaneously. However, these are generally bilaterally revealed. In our case, muscle weakness was limited to the right leg and did not improve after discontinuation of pregabalin. So we excluded disuse and pregabalin as a cause of muscle weakness.
There was no clear basis to exclude other pathologies with localized paralytic symptoms other than HZ. Radiculopathy caused by spinal canal stenosis could not be excluded because MRI examination was not performed. However, we thought there was almost no need to rule out other diseases because symptomatic improvement was observed relatively early from therapeutic intervention. The mechanism by which the herpes zoster virus produces motor paralysis is not clear. Samuraki et al. reported that there are no findings of responsible lesions, such as high signals, only in the dorsal horn and no findings in the anterior horn, despite the presence of paralytic symptoms7). On the other hand, MRI has revealed several findings regarding HZ8–12). Yoshioka et al. reported changes in the anterior horn as well as the dorsal horn of the spinal cord on MRI (Magnetic Resonance Imaging)8). Gupta et al. reported denervation findings in the shoulder muscle9). Therefore, MRI examination should be considered if symptoms are prolonged or exacerbated. There is no effective treatment for motor paralysis due to HZ, and early rehabilitation is fundamental. Antiviral drugs reduce the complication rate of motor paralysis in the acute phase of HZ but have no effect on the amelioration of paralysis13). According to the report by Akiyama regarding the prognosis of motor paralysis due to HZ, full recovery was noted in 5 of 12 patients with paralysis4). In our case, drug discontinuation and rehabilitation were initiated immediately after the examination, and early muscle recovery was noted.
We described a case of motor paralysis associated with HZ in which the cause could be identified by MMT. In patients with HZ accompanied by motor paralysis, Avoidance of movement due to pain delays the detection of paralysis and can be difficult to differentiate from disuse and side effects of drugs even after pain relief. Then, it could be difficult to distinguish motor paralysis caused by HZ from other diseases presenting with dizziness and motor paralysis due to disuse symptoms and side effects of drugs. Thus, it is necessary to perform medical examination using MMT, neurological findings, MRI, and electromyography, as needed. Analgesics should be discontinued if possible. Furthermore, early rehabilitation is effective in ameliorating motor paralysis.
