Cat-scratch disease (CSD) is a self-limiting zoonotic illness. Encephalopathy is the most common neurologic manifestation of CSD. Neuroimaging is usually normal with occasional abnormalities reported in children involving the cerebral cortex and thalamus but not previously described in the basal ganglia. Here we report a 7-year-old boy with CSD encephalopathy who developed choreoathetosis with high intensity changes in basal ganglia on magnetic resonance imaging scan.
Cat-scratch disease (CSD) is a universally encountered, zoonotic illness, caused by the pleomorphic, Gram-negative bacillus Bartonella henselae. It follows a bite, lick or scratch by a cat, usually a kitten, or less commonly by dogs and is usually seen in autumn and winter. Most cases occur in children. The illness typically begins with a skin papule or a pustule 3 to 10 days after contact with the animal. This progresses to a characteristic, painful, regional lymphadenopathy, proximal to the site of the bite. Constitutional symptoms like malaise, fever, anorexia, sore throat and vomiting are often seen. Atypical presentation is seen in 5 to 20% of cases 1 which includes neurologic involvement. Here we report a 7-year-old child with CSD encephalopathy who subsequently developed choreoathetosis associated with unusual basal ganglia changes on the magnetic resonance imaging (MRI) scan.
A 7-year-old boy was referred to his local hospital with a 3-day history of headache, reduced appetite, lethargy, agitation and pyrexia. Swelling in the left axilla had been noticed 5 days before his referral which persisted despite treatment with flucloxacillin and erythromycin. There was no significant past medical history or recent travel abroad. His immunizations were up to date. On admission he was drowsy but well-oriented. He had a firm, mobile, nontender and nonerythematous swelling in the left axilla which measured 2 cm in diameter. The remainder of the examination was normal. He was given intravenous cefotaxime and benzylpenicillin. That day he had a short generalized tonic-clonic convulsion, which prompted intravenous aciclovir therapy. Within a few hours his level of consciousness deteriorated and was transferred to our pediatric intensive care unit.
On admission to our hospital he responded and localized to painful stimulation and only made incomprehensible sounds. A computed tomography (CT) scan of his brain was normal, and cerebrospinal fluid (CSF) contained 10 white blood cells, no red blood cells, 3.6 mM glucose and 0.24 g/l protein. The CSF differential count was not performed because of low white blood cell count. His blood, throat swab and CSF cultures were negative for any bacterial growth. The electroencephalogram showed diffuse high amplitude activity which was suggestive of encephalitis. CSF and serum polymerase chain reaction tests and cultures for herpes simplex viruses I and II, enterovirus, human herpesviruss 6 and 7 were negative. His clinical condition improved, but during the next 48 h he had repeated lengthy convulsions with fluctuating level of consciousness. An MRI scan of head showed bilateral high signal intensities of the basal ganglia on T2 weighted imaging (Fig. 1). Acute demyelinating encephalopathy was considered, and he was treated with prednisolone. Because of the MRI results, a diagnosis of metabolic brain disease was also considered and investigated. His seizures stopped, but he then developed choreoathetoid movements. He was treated with a course of tetrabenazine which did not alter his involuntary movements.
He developed an enlarged liver, palpable 5 cm below the costal margin, with peak alanine transferase of 860 units/l and gamma-glutamyltransferase of 787 units/l. An ultrasound of the abdomen showed a swollen liver with compression of the biliary and portal vein radicles. Further investigations for metabolic disorders, including Wilson’s disease and infections, were negative. The IgG to B. henselae was 1/512 on admission (Day 6 from onset of lymphadenopathy) and 18 days later. Hence the diagnosis of CSD was made. His CSF PCR was negative for B. henselae. On questioning it was found that the family had a kitten at home, but there was no history of trauma from kitten scratches.
The patient was initially unable to walk or talk. However, with physiotherapy and occupational therapy, he developed remarkable coordination on his computer game and on kicking a ball despite his continued choreoathetoid movements. He made steady progress and was discharged after 10 weeks, at which time he was able to walk a few steps. By 26 weeks from admission he was able to walk unaided and write; 1 year later he is able to walk and climb stairs and is back at school. He does continue to have involuntary movements infrequently. The follow-up MRI 6 months after onset of illness showed shrinkage of the putamen and the caudate nuclei.
The incidence of neurologic involvement in CSD varies between 0.17 and 2%. 1 The symptoms develop 1 to 6 weeks after the lymphadenopathy is noticed. Encephalopathy is the most commonly reported neurologic complication. 2 Cat-scratch disease encephalopathy (CSDE), which was first reported by Stevens in 1952, is usually seen in older children, adolescents and adults. 3 Seizures may be the first sign and can be difficult to treat and follow a prolonged course. CSDE can also present with altered sensorium, headache, dysreflexia, nuchal rigidity, abnormal plantar reflex, muscle weakness and optic neuritis. Although the pathogenesis in CSDE is unknown, direct bacterial infection of the nervous system and vasculitis have been postulated. 4
The diagnosis of CSDE is based on history, examination and serologic tests such as indirect immunofluorescent assay to detect IgG antibodies to B. henselae. Polymerase chain reaction is also available at special centers. Electroencephalograms may show a nonspecific encephalitis-like picture, 5 and CSF analysis is usually normal.
Cranial imaging like CT scan and MRI scan are usually normal or show very mild changes. 6 To date 65 patients 7 have been reported with CSD encephalopathy with imaging details. Thirteen of these patients had abnormal imaging either on CT or MRI which included focal changes in the occipital area, thalamus and occipital infarcts or diffuse gray and white matter lesions. Only one human immunodeficiency virus-positive patient who was 39 years of age had unilateral basal ganglia involvement. 7 To our knowledge this is the first report of bilateral basal ganglia involvement on MRI in a child with CSDE.
Most children with CSD have a mild and self-limited course with spontaneous, complete recovery and lifelong immunity to reinfection. 8 Although full recovery is expected, delay in recovery has been related to significant neurologic involvement. This may warrant an extensive rehabilitation program with the active involvement of a multidisciplinary team, as was the case in our patient.
In conclusion CSDE is a rare illness which can cause significant neurologic morbidity and short term sequelae. It has a wide ranging presentation and should be considered in children presenting with unusual neurologic features including choreoathetosis secondary to basal ganglia involvement.
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