Isolated substantia nigra lesions in encephalitis: A specific MRI pattern?
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NEURO-IMAGES
Isolated substantia nigra lesions in encephalitis: A specific MRI pattern? Diogo Goulart Corrêa1 · Roberto Queiroz dos Santos2 · Luiz Celso Hygino da Cruz Jr.1 Received: 13 June 2019 / Accepted: 22 March 2020 © Belgian Neurological Society 2020
Keywords Arbovirus · Dengue virus · Chikungunya virus · Encephalitis · Substantia nigra Lesions in the substantia nigra are manifested by Parkinsonism, and are classically described as rigidity, bradykinesia, shuffling, festinating gait, lack of coordination, and resting tremor [1, 2]. Although several diseases are known to affect the substantia nigra, isolated bilateral substantia nigra lesions detected on magnetic resonance imaging (MRI) have been rarely reported. We present two cases of infectious encephalitis caused by arboviruses that presented with this MRI pattern. A 25-year-old woman presented with fever, cutaneous rash, reduced level of consciousness, and involuntary movement of the upper limbs. The hemogram revealed only thrombocytopenia. Testing for Dengue virus immunoglobulin-M was positive in the cerebrospinal fluid (CSF). Brain MRI showed only bilateral hyperintense signal in the substantia nigra on T2-weighted imaging and fluid-attenuated inversion recovery (FLAIR), without gadolinium enhancement (Fig. 1).
A 7-year-old boy presented with fever, arthralgia, and lethargy. The hemogram showed lymphopenia and thrombocytopenia. Blood immunoglobulin-M testing for Chikungunya virus was positive. Brain MRI demonstrated only bilateral hyperintense signal in the substantia nigra on T2-weighted imaging. After 2 weeks, the patient’s clinical symptoms and MRI-detected alterations had improved (Fig. 2). The tropism of some viruses for the mesencephalon and diencephalon has been previously described. About half of such patients develop Parkinsonism, associated with severe nigral cell loss. However, in general, the spectrum of clinical signs in these patients is greater than that of typical Parkinsonism. Such signs include oculogyric crises, blepharospasm, palilalia, dystonia, chorea, tics, and hiccups, reflecting widespread neuronal damage beyond substantia nigra [3]. The cases presented here showed symmetrical and isolated substantia nigra lesions, a pattern rarely reported in
* Diogo Goulart Corrêa [email protected] 1
Clínica de Diagnóstico por Imagem (CDPI)/DASA, Avenida das Américas, 4666, 302A, 303, 307, 325, 326, Barra da Tijuca, Rio de Janeiro, RJ 2640‑102, Brazil
Hospital dos Servidores do Estado, Rua Sacadura Cabral, 178, Saúde, Rio de Janeiro, RJ 20221‑903, Brazil
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Acta Neurologica Belgica
the published literature. Isolated changes in the substantia nigra have been described in arbovirus encephalitis caused by Saint Louis, Eastern Equine Encephalitis, and Japanese viruses, as well as other pathogens, including Influenza A, Coxsackie, Epstein-Barr viruses, human immunodeficiency virus (HIV), Mycoplasma pneumoniae, and Plasmodium falciparum [4, 5]. Several pathogens are able to enter the central ne
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