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Department of Radiodiagnosis, Government Medical College and Hospital, Sector 32, Chandigarh, IndiaDepartment of Radiodiagnosis, Post Graduate Institute of Medical Education and Research, Sector 12, Chandigarh 160012, India
A 25-year-old male, HIV positive patient was brought to the emergency with altered sensorium, left sided diplopia and right sided motor weakness. No other co-morbidities were elicited on clinical history and examination. A clinical suspicion of Weber’s syndrome was initially suggested. Ophthalmological examination revealed features of complete left sided oculomotor nerve palsy. Blood investigations revealed a CD4 count of 125 cells/mm3. (Normal range: 500–1500 cells/mm3). Non-Contrast CT of the head was normal. MRI brain of the patient revealed multiple T2/FLAIR hyperintense lesions involving grey white matter junction, midbrain, bilateral basal ganglia, left thalamus and the brain stem (Fig. 1), with few of these showing alternate hyper and hypointense zones, consistent with the ‘concentric target sign’ (Fig . 2(A-C)). No diffusion restriction was seen. Post contrast T1 weighted (T1W1) images revealed multiple nodular and ring enhancing lesions with few of these showing an enhancing mural nodule within the ring, consistent with the ‘eccentric target sign’ (Fig. 2(D-F)).
Fig. 1A-D: Axial FLAIR images showing: Multiple round hyperintense lesions involving grey white matter junction of B/L cerebral hemispheres (red arrows in A and B), right basal ganglia (yellow arrow in C), left thalamus (blue arrow in C), brainstem and cerebellar hemispheres (red arrows in D); E-F: Hyperintense lesions on DWI and ADC (red arrows) showing no diffusion restriction.
Fig. 2(A-C): Axial T2 weighted images showing the ‘concentric target sign’ with involvement of the left cerebral peduncle and the ventral midbrain (red arrows in A); right basal ganglia and left thalamus (red arrows in C). (D-F): Axial post contrast T1 weighted images showing: Multiple nodular (red arrows in D) and ring enhancing lesions (red arrows in E); ‘eccentric target sign’ in midbrain on the left (yellow arrow in F).
What is the most likely diagnosis and which part of the oculomotor nerve is involved as denoted by the yellow arrow in Fig.3(B)?
1.
Tuberculoma; fascicular and nuclear portion
2.
Toxoplasmosis; cisternal segment
3.
Lymphoma; cisternal segment
4.
Toxoplasmosis; fascicular and nuclear portion
Fig. 3(A-F clockwise): A-C: Axial DRIVE/CISS (Constructive Interference in Steady State images) showing: A: root exit zone of the left oculomotor nerve (red arrow); B (magnified view of midbrain at superior colliculus level): lesion involving the nuclear and fascicular portion of oculomotor nerve (yellow arrow), with normal nerve at its exit site along the cerebral peduncle (red arrow); C: Cisternal segment of the oculomotor nerve in the interpeduncular cistern (red arrow); D:Sagittal view denoting the cisternal segment (red arrow) coursing between the posterior cerebral artery above (yellow arrow) and superior cerebellar artery below (blue arrow); E: Axial view showing the cavernous portion; F: Sagittal view showing the orbital portion.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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