Herpes Simplex Myelitis: Differences in Clinical Manifestations Between Herpes Simplex Virus Type 1 and Type 2

Various clinical types of central nerve infection caused by herpes simplex virus (HSV) have been identified, and the clinical features of not only encephalitis and meningitis, but also Mollaret meningitis and Elsberg syndrome, have been clarified (Tyler, 2004; Eberhardt et al., 2004). Myelitis is rare, and it has been mostly reported as ascending myelitis, necrotizing myelitis or myeloradiculitis (Klastersky et al, 1972; Koskiniemi et al., 1982; Britton et al., 1985; Tucker et al., 1985; Wiley et al., 1987; Ahmed,1988; Nakagawa et al., 1991; Iwamasa et al., 1991). The initial symptoms of herpes simplex myelitis (HSM) are sensory-motor disturbance of lower limbs and urinary disturbance. Then, transverse myelopathy ascends from level of the lumbosacral spinal cord to level of the cervicothoracic spinal cord. As ascending necrotizing form of HSM often accompanied encephalitis, quadriplegia, or respiratory muscle paralysis, the prognosis of this condition is poor (Table 1). In terms of pathological features, necrotic changes are common, and hemorrhagic lesions are occasionally seen. As a result of technical advances in the 1990s, including diagnostic imaging using MRI and virological diagnosis using PCR, HSM is now more frequently identified. Consequently, in addition to acute ascending myelitis, patients with transverse