Varicella Zoster Myelitis

Varicella zoster myelitis is spinal cord inflammation or infarction from varicella zoster virus reactivation, typically 1 to 2 weeks (up to months) after zoster rash, and occasionally without a rash (zoster sine herpete). It occurs mainly in immunosuppressed people, but also in older adults.

Pathophysiology. The virus spreads from dorsal root ganglia to the cord, causing direct infection, necrosis and vasculopathy with ischaemia.

Subacute progressive or monophasic paraparesis or quadriparesis, sensory level, bladder and bowel dysfunction, and radicular pain at the level of zoster. Features of zoster may be absent. Brown-Sequard syndrome occurs.

Red flags.

• Myelopathy after dermatomal rash, or with HIV.
• Rapid deterioration, urinary retention or respiratory weakness.

CSF shows lymphocytic pleocytosis, raised protein and varicella zoster virus DNA by PCR and anti-varicella zoster virus IgG with an elevated antibody index (more sensitive than PCR later). MRI shows longitudinally extensive or short T2 hyperintensity in the cord, sometimes with enhancement. Check HIV, syphilis and other infectious causes, and antibodies to aquaporin-4 and MOG.

Differential diagnosis.

• Neuromyelitis optica spectrum disorder, multiple sclerosis and MOG antibody disease.
• Herpes simplex virus, cytomegalovirus, Epstein-Barr virus and enteroviral myelitis.
• Cord infarction, syphilis and tuberculous myelitis.

Antiviral. Aciclovir 10 mg/kg IV every 8 hours (adjust to renal function and hydrate) for 14 to 21 days, followed in some cases by valaciclovir 1 g orally three times daily for several weeks.

Corticosteroids. Methylprednisolone 1 g IV daily for 3 to 5 days, given with antiviral therapy, followed by prednisolone taper over 2 to 4 weeks, as suggested by observational data.

Immunosuppressed patients. Prolong treatment until CSF and clinical response, and manage the underlying immunosuppression.

Supportive care. Neuropathic pain treatment (gabapentin 300 mg three times daily, increased as tolerated), bladder care, venous thromboembolism prophylaxis, physiotherapy and respiratory monitoring for cervical lesions.

Prevention. Recombinant zoster vaccine in older and immunosuppressed adults.

Monitoring. Renal function and neurological examination daily during treatment, and repeat MRI.

Referral and escalation. Admit and refer urgently to neurology and infectious diseases.

Special groups. In pregnancy, aciclovir is used for severe disease, with specialist advice.