Imaging findings of LS have been reported in a number of
publications and typical CT-MRI findings have been
considered to be diagnostic hallmark
2,10. Involvement of
the basal ganglia, principally the putamen and the globus
pallidus, is the main diagnostic imaging entity with CT and
MRI
5-11. With MRI; involvement of brain stem,
cerebellum and subthalamic nuclei are also shown, less
commonly involved sides are: Cerebral cortex-white matter
and the substansia nigra
2,5,12. In our case; we had basal
ganglia-brain stem thalamus and subthalamic nuclei
involvement in the brain MRI sections (Fig
1,
2,
3) but
cerebellum-cerebral white and gray matter-substansia nigra
involvement is not seen. Dystonia is the predominant clinical
symptom in the juvenile form of LS
4.
Myo-clonic, tonic-clonic and generalized seizures,
spasm and respiratory disturbances such as apnea-tachypnea
due to brain stem involvement are the other common
symptoms8,9. In our case, she had myo-clonic contractions
in her hands, seizure, vomiting and respiratory disturbances.
There was no spasm and dystonia in the extremities. Proton
MR spectroscopy also play an important role in the diagnosis
of LS12,13. MR spectroscopy performed for the diagnosis
of LS, shows mainly decreased ratio of NAA\Cho and
NAA\Crea, inverted lactate peak at long TE6,7,12. This
finding is consistent with an increased phosphocholine
turnover in the membrane lysis and biosynthesis by the
swollen cells7,14. Decreased NAA is likely due to a
reduction of neurons per unit volume secondary to cell lysis,
attributed to axonal loss, degradation of NAA in injured
neurons and gliosis6,7,15. Increased lactate in LS and
mitochondrial encephalopathies, may be the result of
prevailing glycolysis, possibly in conjunction with cell
hypoxia\ischemia from a possible inadequate blood supply7,14, but increased lactate peak is not specific for LS, it
may be found in acute strokes, seizures, tumors and etc. An
increase in lactate is found in the peripheral blood, CSF and
brain of many patients with mitochondrial encephalopathies12,13. It must be mentioned that normal blood lactate does
not rule out the diagnosis16,17.
Barkovich et al12 reported an increase in lactate at
MR spectroscopy in affected areas of patients, generally
basal ganglia with mitochondrial diseases.In his cases there
were also involvement of cerebral white matter and they
didn't see any increased lactate peak. In our case, we had
also seen inverted lactate doublet from the basal ganglia and
thalamus but our patient didin't have cerebral white matter
lesions. Ducreux et al7 reported a case of acute severe
unusual mitochondrial encephalopathy, lactic acidosis and
stroke like events. For the imaging, he performed MRS, MR
Diffusion tensor imaging and fiber tracking, then confirmed
the diagnosis by muscle biopsy. In his case, the lesions were
shown in the mesencephalon, medulla oblongata, cerebellum
and cervical spinal cord on brain MRI, from the medulla
oblongata with single-voxel spectroscopy via long TE, there
was normal creatine, decreased NAA, inverted lactate peak at 1.3 ppm, increased choline peak. In our case, we had also
similar findings in the MRS but in the brain MRI, medulla
oblongata and cerebellum was not involved. Bowen et al6
reported a mitochondrial encephalopathy case with a
maternally inherited diabetes and deafness (MIDD). There
was extensive subcortical, periventricular white matter and
basal ganglia high signal intensities on T2 weighted MR
studies and mildly increased lactate, increased cho\crea and
mildly decreased NAA\crea ratios in the proton MR
spectroscopy sampled from the periventricular white matter.
He regarded the mild decrease of NAA\Crea ratio as the mild
neuronal damage and mild lactate increase due to the mild
mitochondrial metabolic disruption. In our case, we didn't
see any involvement in the subcortical and periventricular
white matter on MR studies and spectroscopically, we had
inverted lactate doublet and obvious decrease in the
NAA\Crea ratio. In our case the proton MR spectroscopy also
showed increased choline peak and increased Cho\Crea ratio.
Ashrafi et al17 presented 15 cases of LS aged
between 6-156 average 40.5 months. 90% blood lactate is
increased, on MRI studies; 100% symmetric striatal necrosis,
73 caudate nucleus involvement were the most frequent
findings. Cerebral white matter and brain stem involvement
were rare, about 10 percent. Only 1 patient; 13 years old girl
underwent to MRS due to normal blood lactate level, MR
spectroscopy showed abnormal lactate elevation in the basal
ganglia and he concluded that normal blood should not rule
out the diagnosis of LS. Our patient was 10 years old girl
and on T2W images, there was high signaled nodular
intensities in the basal ganglia-thalamus and subthalamic
nuclei. We also saw the abnormal lactate elevation in the MR
spectroscopy of the patient. Grodd et al18 studied
metabolic and destructive brain disorders in children, he had
three cases of LS, they all had metabolic acidosis, increased
lactate and pyruvate concentrations in blood and CSF.
MR studies of them showed bilateral lesions in the
putamen and caudate nuclei. MR spectroscopy revealed
decreased peak intensity for NAA and elevated levels of
lactate in the head of caudate nucleus. In our patient; MRI
and MRS findings were similar but blood lactate level was
normal. As seen in the literature, MRI-MR Spectroscopy
findings conjunction to clinical symptoms and laboratory
findings are noteworthy in the establishment of
Mitochondrial Encephalopathies. In our opinion, the
demonstration of symmetric basal ganglia, brain stem and
subthalamic nuclei involvement in MRI indicates a
mitochondrial disorder in children, the combination of MR
spectroscopy and brain MRI increases the specificity for the
detection of LS especially for the juvenile form. We suggest
that inverted lactate doublet peak –increased choline peak
and decreased NAA\Cho and NAA\Crea ratios with
conjunction to the pathognomonic brain MRI findings and
elevation of lactate in CSF, is enough to diagnose the disease;
have a direct impact on the clinical assessment, care and
treatment of the juvenile form of LS.
)
)
)
)
)