Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 58, Num. 6, 2010, pp. 958-960

Neurology India, Vol. 58, No. 6, November-December, 2010, pp. 958-960

Letter to Editor

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation: A rare white matter disease with characteristic magnetic resonance imaging findings

Anitha Sen¹, Pandurang R Wattamwar², Bejoy Thomas¹, Muralidharan Nair²

¹ Department of Imaging Sciences & Interventional Radiology, SCTIMST, Thiruvananthapuram, Kerala, India
² Department of Neurology, SCTIMST, Thiruvananthapuram, Kerala, India
Correspondence Address: Anitha Sen, Department of Imaging Sciences & Interventional Radiology, SCTIMST, Thiruvananthapuram, Kerala, India, dranithasen@hotmail.com

Date of Acceptance: 17-Aug-2010

Code Number: ni10271

PMID: 21150073
DOI: 10.4103/0028-3886.73766

Sir,

A 23-year-old man born of III degree consanguineous marriage presented with insidious onset gradually progressive decrease in vision in both the eyes, tremors and incoordination. He also complained of stiffness and dragging of both lower limbs while walking since 15 years of age. However, even after 10 years into the illness, he could independently perform all his activities of daily living. On examination, his visual acuity was 6/24 with bilateral primary optic atrophy [[Figure - 1]a and b]. There were bilateral pyramidal signs along with finger-nose incoordination in both upper limbs. His gait was spastic.

Brain and spinal cord magnetic resonance imaging (MRI) showed confluent cerebral white matter changes with relative sparing of 'U'fiber [Figure - 1]c; dorsal and lateral column involvement in cervical and dorsal spinal cord [Figure - 2]d; pyramidal tract involvement in medulla [Figure - 2]c. Also seen involved were posterior limb of internal capsule [Figure - 1]d, medial lemniscus in brainstem [Figure - 2]b, superior cerebellar peduncles [Figure - 2]b and cerebellar white matter [Figure - 2]a. These findings fulfilled 3 major and atleast 3 supportive MRI criteria for leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL). On FLAIR images, white matter abnormalities showed areas of lower signal intensity [Figure - 3]a. White matter diffusion hyperintensity [Figure - 3]b with a complicated apparent diffusion coefficient (ADC) pattern [Figure - 3]c: Low ADC at the border of white matter abnormalities and elevated ADC values in rest of the white matter were seen. MR spectroscopy (MRS) showed increased lactate [[Figure - 1]e and f]. Other investigations: Cerebrospinal fluid (CSF) lactate: 26.8 mg/dL (normal: 10-22); serum lactate: 24.4 mg/dL (normal: 4.5-19.8); visual evoked potential: reduced P100 amplitude; and nerve conduction velocity: normal. Genetic study for mutational gene localization is not available in India.

LBSL is a recently described rare autosomal recessive disorder with gradual onset, usually in childhood or adolescence, but occasionally in adulthood. It is caused by mutations in DARS2 gene on chromosome 1, encoding mitochondrial aspartyl tRNA synthase. MRI findings often suggest the diagnosis. It has previously been reported from Netherlands, ^[1] Turkey, ^[2] Finland, ^[3] Russia, ^[4] Brazil ^[5] and USA. ^[6] To the best of our knowledge, this is the first report from the Indian subcontinent. Optic atrophy has not been reported in LBSL previously. For an MRI-based diagnosis ^[7] of LBSL, all the major criteria and one of the supportive criteria need to be fulfilled. Major criteria - signal abnormalities in the following: (1) cerebral white matter, which is either nonhomogeneous and spotty or homogeneous and confluent, with relative sparing of the 'U' fibers; (2) dorsal columns and lateral corticospinal tracts of the spinal cord; (3) pyramids in the medulla oblongata. Supportive criteria: signal abnormalities in splenium of the corpus callosum, posterior limb of the internal capsule, medial lemniscus in the brainstem, superior cerebellar peduncles, inferior cerebellar peduncles, intraparenchymal part of the trigeminal nerve, mesencephalic trigeminal tracts, anterior spinocerebellar tracts in the medulla, cerebellar white matter with subcortical preponderance.

Areas of lower signal intensity within white matter on FLAIR images and white matter diffusion hyperintensity with a complicated ADC pattern: low ADC at the border of white matter abnormalities and elevated ADC values in rest of the white matter have been reported previously in LBSL. Differential diagnosis on MRI include: (1) vitamin B12 deficiency [no brainstem abnormalities, only cervical spinal cord involved ^[8] as opposed to entire spinal cord involvement in LBSL ^[9] ]; (2) mitochondrial disorders (although brainstem and spinal cord are frequently involved in mitochondrial disorders, the selective involvement of specific brainstem and spinal cord tracts is unique for LBSL ^[9] ). Elevated serum and CSF lactate values, though not essential, support the diagnosis of LBSL. Treatment is supportive: physical therapy and rehabilitation to improve motor function and prevent secondary complications like contractures and scoliosis. ^[10]

In conclusion, distinct brain and spinal cord MRI features should lead to the diagnosis of LBSL, with the help of MRI diagnostic criteria. Primary optic atrophy seen in this case implies that ocular examination be suggested for all LBSL patients.

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