T1 Hyperintensity of the Pediatric Neural Axis: What to Consider?
3-year-old girl with numerous large congenital melanocytic nevi presented with acute onset of right hemiparesis following 6 weeks of morning emesis and intermittent lethargy. On examination, she was lethargic with right hemiparesis and a left partial third nerve palsy with ptosis and miosis. Precontrast T1-weighted magnetic resonance images of the spine demonstrated diffuse hyperintensity along the pial surfaces of the spinal cord (Figure, A). T1hyperintensity is attributed to stable free radicals in melanin, which elicit paramagnetic effects by shortening the T1 relaxation time. Postcontrast T1-weighted images showed
Figure. A, Sagittal T1-weighted image of the spine shows diffuse nodular hyperintensity along the pial surfaces of the spinal cord attributable to melanin deposition (arrows). B, Sagittal T1-weighted postcontrast image of the spine demonstrates leptomeningeal enhancement along the pial surfaces of the spinal cord and nerve root enhancement (arrows). C, Axial postcontrast T1-weighted image of the brain was remarkable for diffuse nodular leptomeningeal enhancement and dilatation of the lateral and third ventricles. D, Sagittal constructive interference in steady state image of the brain shows a patent aqueduct and normal sized fourth ventricle compatible with communicating hydrocephalus.
leptomeningeal enhancement along the spinal cord and nerve root enhancement (Figure, B), consistent with leptomeningeal disease and malignant degeneration. Brain magnetic resonance images were remarkable for diffuse leptomeningeal enhancement and communicating hydrocephalus (Figure, C and D) secondary to leptomeningeal disease, malignant degeneration, and reduction of cerebrospinal fluid absorption at the arachnoid granulations. The patient’s symptoms resolved with placement of a ventricular drain. T1-hyperintensity causes include fat, hemorrhage, calcium, proteinaceous material, minerals, injection of contrast agent, or melanin.1 In this patient, T1-hyperintensity of the spinal cord surface and congenital nevi suggested neurocutaneous melanosis. Neurocutaneous melanosis is a rare sporadic phakomatosis caused by proliferation of melanocytes in the skin and leptomeninges.2 Our patient’s acute neurologic deficits were presumably caused by compression of the corticospinal tracts and third nerve fascicles in the left midbrain because of hydrocephalus. Genetic analysis revealed a NRAS Q61K mutation. Treatment with MEK inhibitor trametinib was initiated, but the patient unfortunately died 11 days later. Though prognosis remains poor, new potential treatments are emerging based on elucidation of molecular pathology underlying the disease.3 In addition to trametinib, which is approved by the Food and Drug Administration for metastatic melanoma in patients with BRAF mutations, other MEK inhibitors, including MEK162; BRAF inhibitors, such as vemurafenib and dabrafenib, are being investigated in patients with RAS pathway mutations.4 n Lisa R. Sun, MD Ryan J. Felling, MD Division of Pediatric Neurology
Andrea Poretti, MD Thangamadhan Bosemani, MD Section of Pediatric Neuroradiology Division of Pediatric Radiology Russell H. Morgan Department of Radiology and Radiological Science The Johns Hopkins University School of Medicine Baltimore, Maryland
References available at www.jpeds.com
J Pediatr 2015;167:497. 0022-3476/$ - see front matter. Copyright ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jpeds.2015.04.046
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