In the nineteenth century, almost every disease of the spinal cord was labeled myelitis. Morton Prince, writing in Dercum’s Textbook of Nervous Diseases in 1895, referred to traumatic myelitis, compressive myelitis, and so on, obviously giving a rather imprecise meaning to the term. Gradually, knowledge of neuropathology advanced, and one disease after another was removed from this category until only the verifiably inflammatory ones remained.
The spinal cord is known to be the locus of a limited number of infective and noninfective inflammatory processes, some causing selective destruction of neurons, others affecting primarily white matter (tracts), and yet another group involving the meninges and white matter or leading to a necrosis of both gray and white matter. Other special terms, qualifying myelitis, are used to indicate more precisely the distribution of the process: if confined to gray matter, the proper expression is poliomyelitis; if to white matter, leukomyelitis. If approximately the whole cross-sectional area of the cord is involved at one or more levels, the process is said to be a transverse myelitis (although the term is still used more broadly for many myelitides); if the lesions are multiple and widespread over a long vertical extent, the modifying adjectives diffuse or disseminated are used and recently longitudinally extensive myelopathy has been introduced to denote a special form of necrotic myelopathy that is associated in most cases with particular circulating autoantibodies (see Chap. 35). The term meningomyelitis refers to combined inflammation of meninges and spinal cord and meningoradiculitis to combined meningeal and root involvement. An inflammatory process limited to the spinal dura is called pachymeningitis, and if infected material collects in the epidural or subdural space, it is called epidural or subdural spinal abscess or granuloma, as the case may be. The adjectives acute, subacute, and chronic denote the tempo of evolution of myelitic symptoms—namely, more or less within days, 2 to 6 weeks, or more than 6 weeks, respectively. The main causes of myelitis are listed below.
Classification of Inflammatory Diseases of the Spinal Cord
I. Viral myelitis (Chap. 32)
A. Enteroviruses (groups A and B coxsackievirus, poliomyelitis, others)
B. Herpes zoster
C. Myelitis of AIDS
D. Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex
E. Rabies
F. Arboviruses-Flaviviruses (Japanese, West Nile, etc.)
G. HTLV-I (human T-cell lymphotropic virus type I; tropical spastic paraparesis)
II. Myelitis secondary to bacterial, fungal, parasitic, and primary granulomatous diseases of the meninges and spinal cord (Chap. 31)
A. Mycoplasma pneumoniae
B. Lyme disease
C. Pyogenic myelitis 1. Acute epidural abscess and granuloma 2. Abscess of spinal cord
D. Tuberculous myelitis (Chap. 31) 1. Pott disease of the spine with secondary cord compression 2. Tuberculous meningomyelitis 3. Tuberculoma of spinal cord
E. Parasitic and fungal infections producing epidural granuloma, localized meningitis, or meningomyelitis and abscess, especially certain forms of schistosomiasis (Chap. 32)
F. Syphilitic myelitis (Chap. 31) 1. Chronic meningoradiculitis (tabes dorsalis) 2. Chronic meningomyelitis 3. Meningovascular syphilis 4. Gummatous meningitis including chronic spinal pachymeningitis