Detection of acute cytotoxic changes in progressive neuronal degeneration of childhood with liver disease (Alpers-Huttenlocher syndrome) using diffusion-weighted MRI and MR spectroscopy

Cerebral imaging in paediatric mitochondrial disorders

OBJECTIVES

Because the central nervous system (CNS) is the second most frequently affected organ in mitochondrial disorders (MIDs) and since paediatric MIDs are increasingly recognised, it is important to know about the morphological CNS abnormalities on imaging in these patients. This review aims at summarising and discussing current knowledge and recent advances concerning CNS imaging abnormalities in paediatric MIDs.

METHODS

A systematic literature review was conducted.

RESULTS

The most relevant CNS abnormalities in paediatric MIDs on imaging include white and grey matter lesions, stroke-like lesions as the morphological equivalent of stroke-like episodes, cerebral atrophy, calcifications, optic atrophy, and lactacidosis. Because these CNS lesions may be seen with or without clinical manifestations, it is important to screen all MID patients for cerebral involvement. Some of these lesions may remain unchanged for years whereas others may be dynamic, either in the sense of progression or regression. Typical dynamic lesions are stroke-like lesions and grey matter lesions. Clinically relevant imaging techniques for visualisation of CNS abnormalities in paediatric MIDs are computed tomography, magnetic resonance (MR) imaging, MR spectroscopy, single-photon emission computed tomography, positron-emission tomography, and angiography.

CONCLUSIONS

CNS imaging in paediatric MIDs is important for diagnosing and monitoring CNS involvement. It also contributes to the understanding of the underlying pathomechanisms that lead to CNS involvement in MIDs.

Case 250: Alpers-Huttenlocher Syndrome

History A 10-year-old girl with global developmental delay and attention deficit hyperactivity disorder was transferred from an outside hospital because of confusion and multiple episodes of left face and arm jerking. Physical examination revealed normal muscle bulk, strength, and tone in the bilateral upper and lower extremities but insuppressible left arm and jaw twitching Lumbar puncture revealed no white or red blood cells, a normal glucose level of 55 mg/dL (3.0 mmol/L) (normal range, 50-80 mg/dL [2.8-4.4 mmol/L]), and an elevated protein level of 81.6 mg/dL (normal range, 15-60 mg/100 dL). A comprehensive metabolic panel revealed lactic acidosis. The patient was initially started on levetiracetam, phenobarbital, phenytoin, and topiramate for status epilepticus. Hepatic dysfunction was not present at initial admission but developed 2 months later, with an alanine aminotransferase level of 90-406 U/L (1.5-6.8 μkat/L) (normal range, 8-37 U/L [0.13-0.62 μkat/L]) and aspartate aminotransferase in the range of 75-187 U/L (1.2-3.1 μkat/L) (normal range, 8-35 U/L [0.13-0.58 μkat/L]). Electroencephalography revealed right parietal and occipital spike-and-wave discharges, with bursts of up to 20 seconds, which were indicative of subclinical status epilepticus. The family history was remarkable for a sister with head lag, developmental delay, seizure disorder, and liver failure.

Central Nervous System Imaging in Mitochondrial Disorders

Imaging of central-nervous-system (CNS) abnormalities is important in patients with mitochondrial disorders (MCDs) since the CNS is the organ second most frequently affected in MCDs and some of them are potentially treatable. Clinically relevant imaging techniques for visualization of CNS abnormalities in MCDs are computed tomography, magnetic resonance imaging, and MR-spectroscopy. The CNS abnormalities in MCDs visualized by imaging techniques include stroke-like lesions with cytotoxic or vasogenic edema, laminar cortical necrosis, basal ganglia necrosis, focal or diffuse white matter lesions, focal or diffuse atrophy, intra-cerebral calcifications, cysts, lacunas, hypometabolisation, lactacidosis, hemorrhages, cerebral hypo- or hyperperfusion, intra-cerebral artery stenoses, or moyamoya syndrome. The CNS lesions may proceed with or without clinical manifestations, why neuroimaging should be routinely carried out in all MCDs to assess the degree of CNS involvement. Some of these lesions may remain unchanged for years, some may show contiguous spread and progression, but some may even disappear, spontaneously or in response to medication. Dynamics of Stroke-like lesions may be positively influenced by L-arginine, dichloracetate, steroids, edavarone, or antiepileptics. Symptomatic treatment of CNS abnormalities in MCD patients may positively influence their outcome.

Alpers syndrome: the natural history of a case highlighting neuroimaging, neuropathology, and fat metabolism

Mitochondrial diseases are increasingly being recognized as causes of encephalopathy and intractable epilepsy. There is no gold-standard test for diagnosing mitochondrial disease, and the current diagnosis relies on establishing a consistent pattern of evidence from clinical data, neuroimaging, tissue biopsy, and biochemical, genetic, and other investigations. Experience in the diagnosis and treatment of patients with certain forms of mitochondrial disease, such as Alpers syndrome, is largely gained from case reports or small case series. The authors describe a case of Alpers syndrome due to POLG1 mutations, including serial neuroimaging and pathological investigations, to illustrate two main points: (1) Unique characteristics evident on serial diffusion-weighted imaging can be a valuable indicator of Alpers syndrome; and (2) abnormal lipid metabolism can be present in Alpers syndrome, which may need to be considered when using a ketogenic diet.

Diffusion-weighted imaging in preclinical Leigh syndrome

We report on a preterm Japanese male baby with Leigh syndrome, i.e., intrauterine growth restriction, central apnea, and feeding difficulty. These signs improved at 41 weeks of corrected age. At that time, brain magnetic resonance imaging revealed increased signal in diffusion-weighted imaging in the parietal white matter, bilaterally and symmetrically not respecting vascular territory or boundaries. However, clinical improvement deterred us from further investigation. About 3 months later, he manifested frequent ictal apnea with myoclonic seizures and deterioration of consciousness to semicoma. Subsequent diffusion-weighted imaging revealed increased signal in the bilateral symmetric thalamus, internal segments of the globus pallidus, substantia nigra, and pontine tegmentum. Laboratory investigation indicated remarkable elevation of lactate levels in cerebrospinal fluid. The diagnosis was of Leigh syndrome. We think this is the first reported case of Leigh encephalopathy with transient abnormality of diffusion-weighted imaging of the white matter before apparent clinical onset. Leigh syndrome should be included in the differential diagnosis of abnormality of diffusion-weighted imaging in white matter without apparent clinical signs.

In vivo 1H magnetic resonance spectroscopy-derived metabolite variations between acute-on-chronic liver failure and acute liver failure

BACKGROUND AND AIMS

Acute-on-chronic liver failure (ACLF), acute liver failure (ALF) and chronic liver disease (CLD) are common forms of liver failure and present with similar clinical profiles. The aim of this study was to compare brain metabolite alterations in all the three groups of patients with controls, using in vivo proton magnetic resonance spectroscopy (MRS), and to look for any significant differences in metabolites that may help in differentiating between these three conditions.

METHODS

Nine patients with ACLF, 10 with ALF, 10 patients with CLD and 10 age-matched controls were studied. The relative concentrations of N-acetylaspartate (NAA), choline (Cho), glutamine/glutamate (Glx) and myoinositol (mI) with respect to creatine (Cr) were measured.

RESULTS

ACLF (3.07+/-0.72), ALF (4.39+/-1.25) and CLD (3.15+/-0.69) patients exhibited significantly increased Glx/Cr ratios compared with controls (2.14+/-0.42). The NAA/Cr ratio was significantly decreased in both ACLF (mean=0.84+/-0.28) and CLD (mean=0.97+/-0.21) patients as compared with that in controls (mean=1.24+/-0.20). No significant difference among ALF, ACLF and CLD patients was noted in the Cho/Cr ratios. ACLF patients showed significantly lower mI/Cr and Glx/Cr ratios compared with the ALF group.

CONCLUSION

In vivo proton MRS-derived cerebral metabolite alterations in hepatic encephalopathy owing to ALF are significantly different from the one owing to ACLF and CLD; these may be due to the differences in the pathogenesis of these two overlapping clinical conditions.

Neuroimaging of mitochondrial disease

Mitochondrial disease represents a heterogeneous group of genetic disorders that require a variety of diagnostic tests for proper determination. Neuroimaging may play a significant role in diagnosis. The various modalities of nuclear magnetic resonance imaging (MRI) allow for multiple independent detection procedures that can give important anatomical and metabolic clues for diagnosis. The non-invasive nature of neuroimaging also allows for longitudinal studies. To date, no pathonmonic correlation between specific genetic defect and neuroimaging findings have been described. However, certain neuroimaging results can give important clues that a patient may have a mitochondrial disease. Conventional MRI may show deep gray structural abnormalities or stroke-like lesions that do not respect vascular territories. Chemical techniques such as proton magnetic resonance spectroscopy (MRS) may demonstrate high levels of lactate or succinate. When found, these results are suggestive of a mitochondrial disease. MRI and MRS studies may also show non-specific findings such as delayed myelination or non-specific leukodystrophy picture. However, in the context of other biochemical, structural, and clinical findings, even non-specific findings may support further diagnostic testing for potential mitochondrial disease. Once a diagnosis has been established, these non-invasive tools can also aid in following disease progression and evaluate the effects of therapeutic interventions.

Homozygous W748S mutation in the POLG1 gene in patients with juvenile-onset Alpers syndrome and status epilepticus

PURPOSE

Polymerase gamma (POLG) is the sole enzyme in the replication of mitochondrial DNA (mtDNA). Numerous mutations in the POLG1 gene have been detected recently in patients with various phenotypes including a classic infantile-onset Alpers-Huttenlocher syndrome (AHS). Here we studied the molecular etiology of juvenile-onset AHS manifesting with status epilepticus and liver disease in three teenagers.

PATIENTS AND METHODS

We examined 14- and 17-year-old female siblings (patients 1 and 2) and an unrelated 15-year-old girl (patient 3) with juvenile-onset AHS, sequenced POLG1, and the entire mtDNA, examined mtDNA deletions by amplification of the full-length mtDNA with the long PCR method and used real-time PCR to quantify mtDNA in the tissue samples.

RESULTS

The initial manifestations were migraine-like headache and epilepsy, and the terminal manifestations status epilepticus and hepatic failure. A homozygous W748S mutation in POLG1 was detected in the three patients. No deletions or pathogenic point mutations were found in mtDNA, but all three patients had mtDNA depletion.

CONCLUSIONS

POLG mutations should be considered in cases of teenagers and young adults with a sudden onset of intractable seizures or status epilepticus, and acute liver failure. The W748S POLG1 mutation seems to lead to tissue-specific, partial mtDNA depletion in patients with juvenile-onset Alpers syndrome. Valproic acid should be avoided in the treatment of epileptic seizures in these patients.

Central nervous system manifestations of mitochondrial disorders

The central nervous system (CNS) is, after the peripheral nervous system, the second most frequently affected organ in mitochondrial disorders (MCDs). CNS involvement in MCDs is clinically heterogeneous, manifesting as epilepsy, stroke-like episodes, migraine, ataxia, spasticity, extrapyramidal abnormalities, bulbar dysfunction, psychiatric abnormalities, neuropsychological deficits, or hypophysial abnormalities. CNS involvement is found in syndromic and non-syndromic MCDs. Syndromic MCDs with CNS involvement include mitochondrial encephalomyopathy, lactacidosis, stroke-like episodes syndrome, myoclonic epilepsy and ragged red fibers syndrome, mitochondrial neuro-gastrointestinal encephalomyopathy syndrome, neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome, mitochondrial depletion syndrome, Kearns-Sayre syndrome, and Leigh syndrome, Leber's hereditary optic neuropathy, Friedreich's ataxia, and multiple systemic lipomatosis. As CNS involvement is often subclinical, the CNS including the spinal cord should be investigated even in the absence of overt clinical CNS manifestations. CNS investigations comprise the history, clinical neurological examination, neuropsychological tests, electroencephalogram, cerebral computed tomography scan, and magnetic resonance imaging. A spinal tap is indicated if there is episodic or permanent impaired consciousness or in case of cognitive decline. More sophisticated methods are required if the CNS is solely affected. Treatment of CNS manifestations in MCDs is symptomatic and focused on epilepsy, headache, lactacidosis, impaired consciousness, confusion, spasticity, extrapyramidal abnormalities, or depression. Valproate, carbamazepine, corticosteroids, acetyl salicylic acid, local and volatile anesthetics should be applied with caution. Avoiding certain drugs is often more beneficial than application of established, apparently indicated drugs.

Mitochondrial respiratory chain deficiencies expressing the enzymatic deficiency in the hepatic tissue: a study of 31 patients

We describe the clinical, biochemical, and molecular characteristics of 31 patients with hepatic respiratory chain deficiencies to suggest possible guidelines for a liver biopsy. Initially, 67% of the children did not have any sign of hepatic dysfunction, and 35% presented exclusively with neurologic symptoms. Initial hyperlactacidemia was severe in 52%. Mortality was high (52%) and more marked in newborns; 28% never developed hepatic disease over time despite long-term follow-up. Hepatic, nonspecific multisystem initial symptoms, and constant hyperlactacidemia had significant statistical value as negative prognosis factors. We conclude that liver biopsy should be considered not only in patients with hepatic involvement, but also in patients with predominant neurologic disorders if there is a suspicion of a mitochondrial respiratory chain defect.

Quantitative evaluation of diffusion-weighted magnetic resonance imaging of focal hepatic lesions

AIM: To explore the quantitative analysis of diffusion-weighted magnetic resonance imaging (DWMRI) in differential diagnosis of focal hepatic lesions.

METHODS: DWMRI was performed in 149 hepatic lesions, including hepatocellular carcinoma (34 cases), hepatic metastases (37 cases), cavernous hemangioma (42 cases), hepatic cyst (36 cases). Apparent diffusion coefficient (ADC) values were evaluated using four different b values in different sequences. The ratio of ADC values of lesion/liver in hepatocellular carcinoma and hepatic metastases was also calculated.

RESULTS: The mean ADC values of hepatic lesions were as follows: hepatocellular carcinoma (0.95 ± 0.11)×10^-3 mm²/s, hepatic metastasis (1.13 ± 0.21)×10^-3 mm²/s, cavernous hemangioma (1.86 ± 0.36)×10^-3 mm²/s, hepatic cyst (3.14 ± 0.31)×10^-3 mm²/s. The ratio of ADC values in lesion/liver in hepatocellular carcinoma was 0.91± 0.11, being significantly different from that in hepatic metastasis (1.21 ± 0.18, P < 0.05).

CONCLUSION: ADC values and quantitative analysis of focal hepatic lesions are of significant values in differential diagnosis of focal hepatic lesions.