Acute disseminated encephalomyelitis, an inflammatory demyelinating disease of the central nervous system, can occur after viral infections or vaccinations. We report the clinical and neuroimaging findings in a 52-year-old man in whom acute disseminated encephalomyelitis developed after accidental self-injection of an industrial hog vaccine. The protracted and progressive clinical course, despite high-dose parenteral corticosteroid therapy, was altered by aggressive plasmapheresis.

Acute disseminated encephalomyelitis (ADEM) is an inflammatory demyelinating disease of the central nervous system (CNS) that is known to occur spontaneously in association with specific and nonspecific viral illnesses and after vaccination against various pathogens. Although it is often a self-limited monophasic illness, the fatality rate is estimated to be as high as 30%, and many patients suffer residual neurologic impairment.Clinical improvement has been reported after initiation of corticosteroid therapy, and relapse has occurred after discontinuation of therapy.We describe a patient with ADEM, possibly related to accidental self-injection of an industrial hog vaccine, and a potential alteration of the clinical course by plasmapheresis.

Disseminated encephalomyelitis: Its variations in form and their relationships to other diseases of the nervous system.

REPORT OF CASE

In mid-February 1992, a 52-year-old farmer had a mild upper respiratory tract infection for 3 weeks. In late February, while vaccinating hogs on his farm, he inadvertently injected himself in the palmar surface of his left hand with approximately 10 mL of a hog vaccine containing pomona bacteria, parvoviras, leptospira, and Erysipelothrix rhusiopathieae (Farrow Sure, SmithKline Beecham, West Chester, Pennsylvania). The vaccine was a killed preparation grown on a swine testicular cell line. Four weeks later, a rapidly progressive encephalopathy developed that was characterized by personality change, agitation, forgetfulness, disorientation, decreased verbalization, and periods of decreased responsiveness. Treatment with methylprednisolone (1 g/day administered intravenously for 14 days) was initiated on April 8, but the patient's condition continued to deteriorate; he became immobile and was abulic. He was transferred to Mayo Clinic Rochester on April 28, 4 weeks after he had initially sought medical treatment.

The patient's medical history was remarkable only for a 10-year history of hypertension controlled with captopril.

On admission to our institution, the patient was unresponsive to verbal commands, moved all extremities spontaneously, showed appropriate withdrawal to painful stimuli, had roving eye movements, and blinked to threat. His pupils were 4 mm in diameter, regular, and reactive. Corneal reflexes were symmetric bilaterally. Findings on funduscopic examination were normal. Deep tendon reflexes were present and symmetric, and plantar reflexes were extensor bilaterally. Tone was increased in the upper extremities. Meningeal signs were absent.

Fig. 1 A and B, Axial magnetic resonance images, demonstrating multifocal subcortical and periventricular areas of increased T2 signal, without mass effect or surrounding edema. C and D, Corresponding axial Tl-weighted images after administration of gadolinium. Magnetic resonance imaging demonstrated multiple foci of increased T2 signal within the subcortical and periventricular white matter of both cerebral hemispheres ( Fig. 1A and B ). Several lesions demonstrated gadolinium enhancement, with little associated mass effect ( Fig. 1 C and D ). Findings on a transfemoral cerebral angiogram were normal. An electroencephalogram revealed persistent polymorphic delta activity consistent with a global disturbance of cerebral function. The cerebrospinal fluid glucose concentration and cell count were normal; protein concentration (93 mg/dL) and IgG synthesis rate (10.11 mg/24 h; normal, less than 8 mg/24 h) were increased, but no oligoclonal bands were present. Results of cytologic tests, fluorescent treponemal antibodies, xanthochromia, and cultures for bacteria and fungi were negative. Results of bacterial, fungal, and viral serologic studies, including human immunodeficiency virus, were negative. A stereotactic brain biopsy of a left periventricular lesion revealed focal perivascular inflammatory demyelination with histiocytes, lymphocytes, and gliosis. No vasculitis, neoplasm, or infection was evident. ADEM was diagnosed.

The patient's condition deteriorated further, and he became comatose. A series of eight plasma exchanges were instituted on May 11 and concluded on June 1; the total plasma volume exchanged was 34,201 mL. On June 2, the patient opened his eyes spontaneously and followed movement. By the second week after the exchanges, he opened his eyes to name, followed simple commands, and spoke short sentences.

By October 1992, the patient was living at home and was independent in most activities of daily living. Trouble-some emotional lability had resolved with administration of amitriptyline. Neuropsychometric testing revealed a moderate impairment in his ability to sustain concentration, learn and remember new information, and reason and solve problems. Language and insight into his cognitive deficits were normal. The patient entered a cognitive rehabilitation program, and by January 1993, he was making important gains in his ability to sustain concentration and learn new information.