F Williams, L Ginsberg, R Brenner, A Cohen
Dr A Cohen, Department of Neurology, Royal Free Hospital, London NW3 2QG, UK; email@example.com
A 70-year-old retired accountant presented with progressive confusion. He was unable to give a clear account of recent events so his wife provided most of the history. She had first noticed four months previously that he had been unable to organise social events for his local Rotary club, and also had lost his ability to manage the household finances. There was then a progressive decline in his memory and organisational skills with increasing confusion about everyday events. In addition he had developed a tremor when holding the newspaper or trying to write. He also complained of muscle cramps in his legs and a band of sensitivity around his abdomen, which were severe enough to wake him at night. He appeared anxious and confused at social occasions, and was sweating and complaining that his head felt hot. The only significant medical history was a raised blood cholesterol for which he was taking simvastatin. There was no relevant family history.
General examination was normal and he was afebrile. On cranial nerve examination he had jerky pursuit eye movements and slow tongue movements. On examination of the limbs he had normal tone, power, reflexes and sensation, but impaired coordination; there was a fine postural tremor in the hands and a bilateral intention tremor, left worse than right. His gait was slow and broad-based. He scored 20/30 on Folstein s Mini-Mental State Examination (MMSE), and 71% on the Addenbrooke s cognitive examination (ACE). Detailed neuropsychological testing showed global cognitive impairment suggesting both cortical and subcortical involvement.
Initial blood tests showed a sodium of 127 mmol/l and a raised ESR (37 mm/h). Further evaluation of the hyponatraemia revealed a low plasma osmolality (268 mOsm/kg) (normal 275 295 mOsm/kg), inappropriately high urine osmolality (676 mOsm/kg) and high urine sodium (67 mmol/l) in the absence of hypovolaemia, confirming the diagnosis of SIADH (Syndrome of Inappropriate AntiDiuretic Hormone secretion). CT and MR scans of the brain were normal.
Figure An erythematous bulls-eye rash, known as erythema migrans.
The diagnosis of Lyme disease may be made clinically on the basis of a history of a tick bite (but only 25 30% of patients with Lyme disease are ever able to recall a tick bite) and the presence of erythema migrans, (although this occurs in only about 80% of patients); clearly a high level of suspicion is needed. We assume the patient developed erythema migrans, although it had disappeared by the time of presentation. The pain in the abdomen was probably truncal radicular pain.
Both serological and CSF tests for anti-Borrelia antibodies were positive in our patient (serum anti-Borrelia IgM positive, IgG reactive; CSF IgG and IgM immunoblot positive) confirming the diagnosis of Lyme disease.
The first line treatment for patients with neurological involvement (Lyme neuroborreliosis) is intravenous ceftriaxone for 2 4 weeks. Early treatment of the disease has a very good prognosis, with most patients experiencing complete relief from neurological symptoms and signs within a few weeks. Our patient was in a late stage of disease, 4 5 months after the initial infection, so his prognosis was less promising. However, after only a week of treatment his MMSE score had improved to 24/30 and he showed continuing improvement over the following weeks. He was given 30 days of intravenous ceftriaxone, with subsequent recovery of the MMSE to 28/30 and ACE to 94/100 at 6 months, with only mild residual frontal and left temporal dysfunction on cognitive testing. He had very little recollection of the events during his illness.
The history should be revisited in all unclear cases, especially in confused patients. Direct questioning may be necessary to elicit certain points, such as a history of a tick bite, as the patient may not see them as relevant to their symptoms.
Lyme encephalopathy is important to consider in cases of dementia because it is highly treatable; it may also present with SIADH.
The diagnosis is confirmed by serological and/or CSF evidence of an antibody response to the causative organism, Borrelia burgdorferi.
Treatment with intravenous ceftriaxone may be very effective in resolving the neurological manifestations of the disease.
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