Chameleon in the brain

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CASE HISTORY A 53-year-old man with supraglottic squamous cell carcinoma, cT3N2bM0, Stage IVA with Eastern Cooperative Oncology Group (ECOG) performance status (PS) 1 at baseline, presented with drowsiness and altered sensorium, on day 3 of starting the first cycle of neoadjuvant chemotherapy (docetaxel + cisplatin). Contrast-enhanced magnetic resonance imaging (MRI) of the brain revealed subcortical white matter edema in the left frontal region, which was hypointense on T1-weighted (T1W) images and hyperintense on T2W and T2 fluid-attenuated inversion recovery (FLAIR) images, with an enhancing sub-centimeter focus within [Figure 1a and b]. Metabolic abnormalities (hyponatremia: serum sodium was 119 mmol/L; normal range: 136-145 mmol/L) were corrected (with 3% normal saline), but the neurological status (altered sensorium) of the patient remained unchanged. Metastasis was considered the likely diagnosis, in view of the presence of disproportionate perilesional edema, and based on this, the patient was continued on the same chemotherapy regimen for four cycles. To assess for disease progression, a repeat MRI was planned in 2 weeks. Unexpectedly, the contrast-enhanced MRI showed multiple ring-enhancing lesions scattered throughout the cerebral hemispheres and cerebellum with associated subcortical white matter edema in bilateral frontal, parietal, and occipital regions, appearing hypointense on T1W images and hyperintense on T2W and T2 FLAIR images. T2 hypointense scolex was seen within the T2 hyperintense lesions [Figure 1c-f]. On enquiry with the relative, a history of pork consumption with tapeworm infection 10 years ago was elicited.Figure 1: (a,c,d): On pretherapy magnetic resonance imaging (MRI) Axial T2-weighted MRI showing subcortical T2 hyperintense white matter edema in bilateral frontal, parietal, and occipital regions surrounding few sub-centimeter-sized lesions (c and d) with T2 hypointense rim. (e,b,f): Axial T1 post-contrast MRI image showing peripherally enhancing (ring enhancing) lesions in areas with edema, scattered in both cerebral hemispheresWhat is the diagnosis, and what should be done next? Once you have finalized your answer, please read on. DIFFERENTIAL DIAGNOSIS AND FURTHER MANAGEMENT The differential diagnosis of ring enhancing lesions includes a list of conditions as described in Table 1. However, the presence of a T2 hypointense scolex with the simultaneous presence of lesions at different stages in the appropriate clinical scenario confirmed the diagnosis of neurocysticercosis. Considering neurocysticercosis as the etiology of the ring-enhancing lesion, a workup including chest, upper, and lower limb radiography was done. Lower limb radiograph revealed multiple rice grain-like opacities scattered in the soft tissues of the bilateral thighs, suggestive of cysticerci [Figure 2]. The patient was started on steroids and antiepileptics for the neurocysticercosis. An MRI done after steroid therapy showed a significant reduction in the perilesional edema, size, and number of enhancing nodular lesions in the cerebral and cerebellar hemispheres, with significant improvement in symptoms and no recurrent neurological episodes, which was indicative of response to therapy [Figure 3].Table 1: Differentials of ring enhancing lesions and key magnetic resonance imaging features (adapted)[ 8 ]Figure 2: Radiograph of bilateral lower limbs showing multiple rice grain-like opacities scattered in the soft tissues of the bilateral thighsFigure 3: (a,b): Three months post institution of steroid therapy. T2-weighted axial magnetic resonance imaging (MRI) showing decrease in previously seen perilesional edema. (c,d): Axial T1 post-contrast MRI images showing marked reduction in number and size of previously seen ring-enhancing lesionsFINAL DIAGNOSIS Neurocysticercosis, in a patient with locally advanced non-metastatic supraglottic carcinoma on neoadjuvant chemotherapy. DISCUSSION Neurocysticercosis is one of the most prevalent parasitic infections of the central nervous system. It is listed by the World Health Organization as a neglected tropical disease affecting around 50 million people globally and the cause of 50,000 deaths annually.[1] It is endemic in tropical and developing countries, including India.[2,3] Cerebral parenchymal involvement is manifested as clearly marginated cysts with an eccentrically situated scolex and marked perilesional edema.[4] In the present report, we describe a case of incidentally diagnosed neurocysticercosis in a patient with a known malignancy. Neurocysticercosis is caused by the parasitic agent Taenia solium. It is common in endemic areas and can involve the nervous system, muscles, and soft tissues. Our patient was a native of Assam, which is a state in northeast India that is endemic for cysticercosis. When interpretating the CNS imaging, a detailed history of the epidemiological setting should be obtained.[5] Neurocysticercosis may present with a wide variety of symptoms ranging from asymptomatic cases to focal neurological deficits and seizures. Stages include non-cystic, vesicular, colloidal vesicular, granular nodular, and calcified.[6] Perilesional edema is most pronounced during the colloidal vesicular and granular nodular stages. The granular stage shows ring enhancement, with minimal edema. The presence of a scolex is characteristic of the vesicular stage and is considered diagnostic. Serological tests, including immunoblot assays, are difficult to access in developing countries, and diagnosis is primarily imaging-based.[7] Metastatic lesions are commonly seen in the grey-white matter junction and are associated with marked perilesional edema. Ring enhancement is a common pattern.[8] Multiple ring-enhancing lesions in the brain can have a varied etiology including infectious, neoplastic, vascular, and inflammatory, as summarized in Table 1.[8] In a patient who has already been diagnosed with a malignancy, it can be difficult to characterize these lesions on imaging. Misinterpreted imaging can lead to delayed and inappropriate treatment. It is difficult to differentiate perilesional edema from metastatic lesions. In our patient, the single enhancing intracranial lesion with edema pointed toward metastasis as the diagnosis. However, worsening of the disease after chemotherapy prompted careful elicitation of the patient’s history and consideration of an alternative diagnosis. After initiation of appropriate therapy, the rapid response of the lesion and an improvement in the clinical status were observed. This indicates the importance of including a broad set of differential diagnoses, even in cases of malignancy, where we may, by default, lean toward metastases as the primary diagnosis. CONCLUSION When a ring-enhancing brain lesion is detected in a patient who had a known diagnosis of malignancy, careful evaluation of the patient’s history and the epidemiological setting is essential to rule out neurocysticercosis and other differential diagnoses. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published, and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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