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A man in his late 60s presented to the emergency department with right leg weakness and a rash across his right medial thigh for the past 10 days. He described the rash as painful and extremely sensitive to touch. His medical history was notable for a renal transplant 35 years ago. He took methylprednisolone and mycophenolate mofetil for immunosuppression.
On physical examination, he was noted to have numerous vesicles superimposed on an erythematous background along the L2-L4 dermatome (figures 1 and 2). The musculoskeletal examination revealed weakness at the right hip and knee with decreased range of motion. Strength was preserved in the left leg and bilateral upper extremities. Patellar reflex was absent on the right and present on the left. No hyper-reflexia was noted. He denied experiencing any urinary or faecal incontinence. After initial assessment of the patient, suspicion was high for herpes zoster. A herpes simplex virus (HSV) PCR test and varicella zoster virus (VZV) PCR test were ordered. The patient was placed on contact precautions. Neurology was also consulted for the right leg weakness. Given the lack of red flag symptoms and confinement of neurological symptoms to a single dermatome/myotome/nerve, an MRI was not deemed necessary.
VZV was detected on PCR, confirming a diagnosis of herpes zoster. Herpes zoster is most classically characterised by a unilateral, painful vesicular rash that can be traced to a specific dermatome.1 VZV remains dormant in the dorsal sensory root ganglion, which lies within close proximity to the ventral motor nerve root. When the ventral motor nerve root is affected, paresis of the motor unit occurs manifesting as weakness or paralysis.
The patient was given a diagnosis of zoster paresis affecting the L4 femoral nerve branch based on his positive VZV test and neurological exam. Zoster paresis is not a very common condition, affecting only 3%–5% of patients with herpes zoster.2 The exact pathogenesis underlying the motor dysfunction is still being debated. Some believe that the virus likely spreads to the ventral motor nerve root, whereas others postulate it is more likely the result of local inflammation.3 4 This patient’s immunocompromised state and advanced age put him at increased risk. A decrease in cell-mediated immunity, as seen with immunosuppressive drugs and older age, is associated with an increased risk for reactivation of VZV.
The patient was treated with intravenous acyclovir at 600 mg every 24 hours, renally dosed. He remained on intravenous acyclovir for 7 days before transitioning to an oral tablet of valacyclovir 1000 mg daily. He remained on this oral dose for 9 days before switching to a 500 mg tablet of valacyclovir given every other day. Physical therapy was consulted, and he understood that it would likely take several months to achieve his baseline strength. Full motor recovery occurs in about 75% of patients with zoster paresis.2 He was still experiencing right leg weakness and his vesicular rash had largely scabbed over at the time of discharge to a subacute rehabilitation centre. The patient died of an unrelated illness months later.
Zoster paresis occurs when reactivation of the VZV spreads to the ventral motor nerve root, leading to paresis. When patients on chronic immunosuppressive therapy contract herpes zoster, they are at an increased risk of developing zoster paresis.
If a patient presents with symptoms of zoster paresis, inpatient antiviral treatment and physical therapy should be initiated immediately to prevent worsening of symptoms.
It is important to ensure that patients with zoster paresis have realistic expectations of when to expect a return to baseline strength. About 75% of patients with zoster paresis reach a full motor recovery after months of therapy.
Patient consent for publication
We would like to acknowledge the patient’s family for allowing us to share his story. Thank you to Dr Rahnama-Moghadam for overseeing this work.
Contributors EA wrote the manuscript with support from all authors. JW and SRM saw the patient and conceived of the idea for this write-up. SGD assisted with editing the manuscript. JW obtained consent from next of kin. SRM supervised all aspects of this work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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