Bickerstaff brainstem encephalitis after heat stroke

Abstract

Sirs: Bickerstaff brainstem encephalitis (BBE) is characterized by acute onset of ophthalmoplegia and ataxia with symptoms and signs indicative of involvement of the central nervous system such as consciousness disturbance [1]. It has been proposed that BBE, Miller Fisher syndrome, and Guillain-Barre syndrome (GBS) are related disorders [8–10]. In fact, a considerable number of patients with BBE have overlapping GBS [8, 15]. A number of factors have been described as triggers of GBS [13]. Heat stroke produces a wide variety of neurological complications [6], but only one case of GBS after heat stroke has been reported [11]. We present a patient with overlapping BBE and GBS after heat stroke. To our knowledge, this is the first report of such a patient. A previously healthy 43-year-old man experienced generalized tonic seizure with loss of consciousness during hard physical work on a hot summer day. He was transferred to our intensive care unit. The core temperature was 42.8°C, heart rate 173 bpm, and blood pressure 66/36 mmHg. Deep coma and bilateral miotic pupils were observed. Laboratory tests showed a platelet count of 113.000/mm3, creatinine 2.73 mg/dL, creatine kinase 2833 U/L, and serum interleukin-6 8594 pg/ml (normal < 4). He was treated with surface cooling (35 °C), mechanical ventilation, intravenous dopamine, and continuous hemodiafiltration. His general status gradually improved. On day 8, he was weaned from mechanical ventilation. On day 9, he was fully conscious with no weakness in the limbs, normal external ocular movements, and normal tendon reflexes. The next day, he again showed consciousness disturbance and weakness in all four limbs. On day 11, he was drowsy, but he was able to respond to commands. His pupils were equal (3.0 mm) and pupillary light reflexes absent. There were complete external ophthalmoplegia, bilateral facial palsy, aphonia, tetraparesis (MRC grade 3 for the upper extremities, grade 2 for the lower ones), limb ataxia, and areflexia. Laboratory examinations on day 12 revealed near-normal blood cell count (white blood cell, 9.900/mm3), and normal serum electrolytes and vitamin B1 levels. Brain MRI found no obvious abnormalities responsible for his consciousness disturbance and muscle weakness. Serum antibodies against ganglioside GM1, GD1a, GT1a, or GQ1b were negative. Cerebrospinal fluid (CSF) contents on day 12 were normal (cell count, 0/mm3; protein level, 21 mg/dl), and a follow-up CSF examination on day 30 revealed the slightly increased protein level (43 mg/dl; normal < 40 mg/dl). Nerve conduction studies (NCS) showed slightly decreased compound muscle action potential (CMAP) amplitudes, normal nerve conduction velocities and distal latencies, and absent F-waves in all the nerves tested (the median, ulnar, peroneal, and tibial nerves). He underwent plasmapheresis 4 times, every other day from day 15. After this treatment, his neurological symptoms were gradually improved. On day 24, he could talk, but his speech was slurred and ataxic. On day 35, when his muscle strength was near-normal, NCS revealed restored F-waves and increased CMAP amplitudes. On day 60, he was discharged to a rehabilitation facility because he was still unable to stand independently due to ataxia. This patient was characterized by acute consciousness disturbance, ophthalmoplegia, facial palsy, tetraparesis, and ataxia, 7 days after heat stroke. After treatment with plasmapheresis, the signs gradually lessened, resulting in a monophasic course. Although several diseases including Wernicke’s encephalopathy, infectious brainstem encephalitis, and GBSlike syndrome by severe exertion [16] should be considered in the differential diagnosis, his clinical features met the criteria for BBE and overlapping GBS [8, 15], suggesting that the disorders may have been triggered by heat stroke. The absence of F-waves during tetraparesis and their restitution in the recovery phase are consistent with proximal conduction block [7]. Pfeiffer reported the only case of GBS after heat stroke, and speculated that heat stroke activates the immune system by cytokine release which opens the blood-nerve barrier and exposes peripheral nerve antigens, thereby inducing GBS [11]. In fact, various cytokines including tumor necrosis factoralpha and interleukin (IL)–6 are conjectured to function in the pathogenesis of heat stroke [2, 4], and also of GBS and related diseases [3, 5, 12, 14]. Elevated serum IL-6 was detected in our patient. Hypercytokinemia may be the key to the association of GBS and related diseases with heat stroke. LETTER TO THE EDITORS