Teaching Case

A 21-year-old man presented with bilateral paresthesia in the lower limbs, ophthalmoplegia, and facial paresthesia in the emergency room. The patient had a previous neurological clinical course of focal deficits and a previous MRI with multiple encephalic lesions. Imaging studies and a lumbar puncture were requested for evaluation.

3T MRI showed multiple oval lesions with T2/FLAIR hypersignal with a periventricular distribution (Figs. 1a, 1b); adjacent to the cortex (Fig. 1c); in the posterior fossa (Fig. 2a) and spine (Fig. 2b). There were central venous vascular structures (central vein sign) within some of the lesions, demonstrated on SWI (Fig. 3) and FLAIR/SWI fusion images (Figs.  4a, 4b, and 4c).  Some lesions presented contrast enhancement (Figs. 5a, 5b, and 5c). The present MRI showed new T2/FLAIR-hyperintense lesions compared to the previous examination.

Additionally, 3T MRI demonstrated extensive cranial nerve involvement, especially III, IV, V, and VI. FLAIR showed hypersignal notably in the trigeminal nerves (Figs. 6a and 6b). There were multiple cranial nerve thickening and diffuse contrast enhancement of the oculomotor, trochlear, trigeminal, and abducens nerves (Figs. 7a, 7b, and 7c).

Multiple sclerosis (MS) has high morbidity, and radiologists should dominate its imaging features to diagnose and define the active disease. The McDonald's criteria for MS defines its spread over time and space on MRI [1,2]. The dissemination in time is contrast-capturing and non-capturing lesions in the same study or the presence of new lesions in subsequent studies [2]. The dissemination in space is specified by lesions in at least two of the following four regions: periventricular, juxtacortical, posterior fossa, and medulla [1,2]. In this case, there was dissemination in time and dissemination in space.

FLAIR plus SWI fusion aids in identifying the lesions with perivenular distribution pattern (central vein sign) [3,4], with high sensitivity and specificity (95% and 92%) for MS diagnosis. Another classic MS involvement is optic neuritis, usually adjacent to the eyeballs [4,5].

The contrast nerve enhancement (CNE) of other cranial nerves in MS is present in about 8% of patients. It is frequently related to unilateral enhancement in the root entry/exit zone (REZ).  In addition, lesions in these zones always preceded the CNE.  A tract-related myelin disintegration due to anterograde trans-synaptic neurodegeneration could explain this mechanism [6]. However, the involvement of multiple cranial pairs is much less frequent in MS. This finding is related to earlier diagnosis of the disease, more aggressive course, a shorter interval between outbreaks, and more significant lesional burden [6]. It is essential to highlight that higher field strengths are more sensitive to detect qualitative and quantitative CNE by MRI [1,2,6].

Additionally, it is essential to exclude other differential diagnoses of demyelinating diseases and multiple cranial nerve enhancement, including tumoral and inflammatory/infectious diseases. The patient was HIV-negative and was not in treatment with natalizumab, which could be related to progressive multifocal leukoencephalopathy [5,7]. In this case, a lumbar puncture excluded infectious etiologies, with extensive negative PCR viral analysis, a non-bacterial biochemical pattern, and was also negative for anti-AQP4-IgG. The only positive finding in the CSF was oligoclonal bands. Other imaging exams like chest and abdomen CT do not demonstrate tumour or inflammatory/infectious diseases.

Finally, the presence of MS clinical course, MRI findings with dissemination in time and space, and no better explanation confirmed the diagnosis. The radiologists should be aware of this pattern, actively searching for MS-associated multiple cranial nerve enhancement due to the clinical and prognostic relevance.