TEST YOUR KNOWLEDGE: Radiology quiz

A child with acute onset of neurological signs

Anne Mitchell, MBBS, FRACR, is consultant radiologist, Department of Radiology, Austin and Repatriation Medical Centre, and Royal Children’s Hospital, Victoria.

An eight year old boy presented with a short history of a b headache, vomiting, drowsiness and increasing left sided weakness, following an episode of a flu-like illness one week earlier. On examination he was drowsy, with neck stiffness, a left hemiparesis, and mild right sided weakness. His initial CT scan is shown (Figure 1 a, b). A lumbar puncture revealed a mildly increased protein level and a normal cell count. MRI was subsequently performed (Figure 2 a, b, c). He was commenced on steroids and showed rapid improvement of neurological signs. a Figure 2a) b) c). MRI showing multiple lesion

Figure 1a) b). CT scan showing multiple lesions

Question 1 D. multiple sclerosis The imaging findings shown in E. all of the above. Figures 1 and 2 are: Question 4 A. multiple lesions with little mass effect Which of the following statements are true? involving white matter only A. ADEM does not occur in adults b B. multiple lesions with no mass effect B. The presence of contrast enhancement involving white matter and deep grey would indicate that tumour is more likely matter than demyelination C. multiple periventricular lesions C. The diagnosis of ADEM can usually be D. multiple mass lesions. made by a combination of typical clinical Question 2 presentation and imaging findings What is the most likely diagnosis? D. MRI is more sensitive than CT for cerebral A. acute viral meningitis lesions of ADEM B. acute disseminated encephalomyelitis E. Cerebral abnormalities in ADEM are due (ADEM) to demyelination and usually resolve. c C. acute viral encephalitis Question 5 D. gliomatosis cerebri or multifocal gliomas. ADEM may follow: Question 3 A. exanthematous viral illnesses The differential diagnosis of the imaging findings B. vaccination includes: C. mycoplasma infection A. cerebral vasculitis eg. systemic lupus ery- D. no preceding illness thematosis (SLE) E. all of the above. B. toxin exposure C. progressive multifocal leukoencephalitis (PML)

Reprinted from Australian Family Physician Vol. 31, No. 9, September 2002 • 1 n A child with acute onset of neurological signs

Answers

1. Answer B In older adults, patchy white matter postimmunisation. It is rarely seen after Both CT and MRI images show multiple abnormality related to hypertension and mycoplasma or other bacterial infection, abnormalities. Several large lesions are aging may have a similar appearance. and in some cases no precipitating cause seen in the deep cerebral white matter, is identified. 4. Answer but there is also bilateral involvement of AFP the thalami. There is no significant mass A. False effect associated with these abnormalities. ADEM usually occurs in children or young adults, but can be seen in much older 2. Answer B patients. The combination of an acute neurological B. False illness following a viral infection, with While enhancement following IV contrast asymmetrical bilateral lesions in white and mass effect are typical features of matter, deep grey matter and occasional tumours, both these features are brain stem and spinal cord involvement is sometimes seen in regions of acute typical of acute disseminated demyelination (in ADEM and MS), due to encephalomyelitis (ADEM). Uncomplicated inflammatory alteration of the blood–brain viral meningitis typically has no focal barrier and oedema. neurological signs and normal MRI. Viral encephalitis eg. herpes simplex type 1 C. True (HSV-1) is an important diagnosis to The diagnosis of ADEM is generally made consider and treat early. It typically on the basis of a monophasic illness produces temporal and inferior frontal grey following viral infection or vaccination, CSF and white matter abnormality on imaging, analysis, imaging studies, and the absence but in equivocal cases, antiviral therapy is of other definable conditions. In some often instituted before other results are cases it may be difficult to distinguish available. Multifocal gliomas could cause ADEM from MS, leukodystrophy, or white matter and thalamic infiltration, and mitochondrial disorders. could present as an acute illness, but D. True tumours often have more mass effect and CT may show abnormalities as in this case patchy irregular contrast enhancement. (Figure 1), but is relatively insensitive. False negatives occur, and CT is unlikely to 3. Answer E show the full extent of the abnormalities. The imaging features of ADEM are nonspecific, and require clinical E. True correlation. The differential diagnosis is The prognosis of ADEM is usually good, very long, and includes: with the highest morbidity (around 10%) in • CNS infections eg. HSV-1 encephalitis, the first week of the illness. The MRI PML (caused by papovavirus in lesions usually resolve within a few weeks, immunocompromised patients), human responding rapidly with steroid therapy. immunodeficiency viral (HIV) Some lesions resolve more gradually over encephalopathy, subacute sclerosing 6–18 months after the onset of panencephalitis symptoms, and organise into glial scars. Approximately 10–30% of patients have • noninfectious inflammatory conditions some permanent neurological deficit. If the eg. multiple sclerosis (MS), cerebral number of the lesions increases on long vasculitis (eg. SLE) and other collagen term follow up, or if the patient develops vascular disorders new neurological symptoms, then MS is • cerebral infarction the more likely diagnosis. • toxin exposure 5. Answer E • metabolic leukoencephalopathies and mitochondrial disorders ADEM is an immune mediated disorder causing perivenous inflammation and • trauma demyelination. It often occurs days to • tumour weeks after a systemic viral infection • radiation or chemotherapy injury. (measles, rubella, varicella, Epstein-Barr virus, mumps, pertussis, influenza, herpes simplex, herpes zoster) or

2 • Reprinted from Australian Family Physician Vol. 31, No. 9, September 2002