Neurocutaneous Melanosis with Bilateral Temporal Lobe Lesions without Leptomeningeal Enhancement: A Distinct Entity or Subtype.

Neurocutaneous melanosis (NCM) is a rare congenital disorder. Most of the cases described in literature for this entity have involvement of the leptomeninges and other structures of brain such as brain stem, temporal lobes, and spinal meninges and no involvement of leptomeninges and presence of lesions in bilateral temporal lobes. NCM without the involvement of leptomeninges should be considered a distinct entity as the prognosis is favorable as compared to cases with leptomeningeal involvement who develop early hydrocephalus and multiple cranial nerve palsies.

ARTICLE

Neurocutaneous melanosis (NCM) is a rare congenital disorder characterized by multiple (greater than three) or giant melanocytic nevi of the skin with lesions in the brain involving the leptomeninges or the brain parenchyma. Most of the cases described in literature have involvement of leptomeninges and other structures of brain such as brain stem, temporal lobes, and spinal meninges. However, only five cases are reported in literature of NCM without the involvement of leptomeninges.[12345] The presences of lesions in the bilateral temporal lobes have been described in literature but to the best of our knowledge, only one such case has been reported till now.[5] Hence, this case becomes unique because of two reasons: no involvement of leptomeninges and presence of lesions in bilateral temporal lobes.

A 6-month-old male infant presented with a history of two episodes of generalized tonic clonic seizures within 1 month. No history of trauma, fever, or any other neurological symptoms was reported. On general examination, the infant had multiple hyperpigmented patches all over his body with largest patch over trunk and buttocks [Figure 1A and B]. The patch over right preauricular region had hair associated with lesion [Figure 1C]. The infant had no focal neurological deficits. Examination of the eyes revealed no lesions. Contrast-enhanced magnetic resonance imaging revealed bilateral lesions in region of mesial temporal lobes (left larger than right), which was hyperintense on T1-weighted scan [Figure 2A], hypointense on T2-weighted scan [Figure 2B], and without any post-contrast enhancement [Figure 2C] or any perilesional edema. The infant was managed with antiepileptic for the control of seizures and was kept on regular follow-up for any change in the size of lesions or any mass effect as the parents were not willing for any neurosurgical intervention in view of no focal neurological deficits or evidence of mass effects on imaging. Stereotactic biopsy and further adjuvant were advised but parents of the infant were not willing for even this minimally invasive procedure. At 1-year follow-up, the infant was seizure free on single antiepileptic, and the lesion had not shown any increase in size on neuroimaging.

Figure 1

(A) Multiple pigmented lesions all over the body. (B) Largest lesion over trunk. (C) Pigmented patch with hair over right preauricular region

Figure 2

(A) Axial image showing hyperintense lesions already marked with arrow in the image. (B) Hyperintense lesionon T2 weighted image already marked with arrow. (C) Lesion already marked with arrow

NCM is a rare, neuroectodermal dysplasia first described by Rokitansky[6] in1861. The classical definition of NCM[7] includes one leptomeningeal melanosis or a central nervous system melanoma, large or multiple congenital nevi in association with meningeal melanosis or melanoma, no evidence of cutaneous melanoma except in patients in whom the examined areas of the meningeal lesions are histologically benign, and no evidence of meningeal melanoma except in patients in whom the examined areas of the cutaneous lesions are histologically benign.[8] In the series of 39 patients reported by Kadonaga and Frieden,[8] only one had normal meninges.

Eaves et al.[4] suggested that primary brain melanoma without diffuse leptomeningeal involvement in patients with giant intradermal nevi is a variant of NCM. The uniqueness of the case lies in the facts that there was no leptomeningeal involvement (only five cases of NCM without the involvement of leptomeninges have been described in literature) and the presence of the lesions in bilateral temporal lobes. To conclude, we would like to propose that cases of NCM without the involvement of leptomeninges should be considered a distinct entity as the prognosis is favorable as compared to cases with leptomeningeal involvement who develop early hydrocephalus and multiple cranial nerve palsies.

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Conflicts of interest

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