Differentiating Genetic Forms of Pontocerebellar Hypoplasia From Acquired Lesions Resembling Pontocerebellar Hypoplasia: Clinical, Neurodevelopmental, and Imaging Insight From 19 Extremely Premature Patients.

It is well established that extreme prematurity can be associated with cerebellar lesions potentially affecting the neurologic prognosis. One of the commonly observed lesions in these cases is pontocerebellar hypoplasia resulting from prematurity, which can pose challenges in distinguishing it from genetically caused pontocerebellar hypoplasia. This confusion leads to unacceptable and prolonged diagnostic ambiguity for families as well as difficulties in genetic counseling. Therefore, it is crucial to identify the clinical and neuroradiologic features allowing to differentiate between acquired and genetic forms of pontocerebellar hypoplasia in order to guide clinical practices and improve patient care. In this regard, we report in the present manuscript the clinical, developmental, and radiologic characteristics of 19 very premature children (gestational age <28 weeks, now aged 3-14 years) with cerebellar lesions and discuss the causal mechanisms. Our findings support the notion that a combination of specific clinical and radiologic criteria is essential in distinguishing between acquired and genetic forms of pontocerebellar hypoplasia.

Postnatal Brain Growth Patterns in Pontocerebellar Hypoplasia.

BACKGROUND: Pontocerebellar hypoplasia (PCH) is a rare group of disorders mainly affecting the cerebellum and pons. Supratentorial structures are variably involved. We assessed brain growth patterns in patients with the most frequent forms of PCH, namely PCH1B (OMIM#614678) and PCH2A (OMIM#277470), since in these types of PCH, pre- and postnatal neurodegeneration is established by neuropathological profiling. To assess the influence of the different pathomechanisms on postnatal growth patterns, we included CASK-associated microcephaly and PCH (MICPCH, OMIM#300749) patients in our analyses, as MICPH mimics PCH on magnetic resonance imaging (MRI) but represents a developmental disorder including abnormal neuronal migration. METHODS: A total of 66 patients were included: 9 patients with PCH1B, 18 patients with PCH2A, 6 patients with MICPCH, and 33 age- and gender-matched hospital-based controls. Segmentation of the vermis and cerebellum was performed manually, as were measurements of the thickness of the head of the caudate nucleus, the width of the anterior horn, and lateral ventricle size. RESULTS: The cerebellum was severely hypoplastic at birth in all patients, and postnatal growth was nearly absent. In patients with PCH1B/2A, we found relative sparing of the vermis compared with the cerebellar hemispheres. In addition, PCH1B and PCH2A cases demonstrated thinning of the head of the caudate nucleus, an associated increase in anterior horn width, and an increase in lateral ventricle size. None of these features were seen in the MICPCH group. CONCLUSIONS: Our findings confirm the progressive nature including caudate nucleus atrophy in PCH1B and PCH2A. In MICPCH, the relative sparing of supratentorial structures confirms its different pathomechanism.

[Early onset epileptic encephalopathy caused by mitochondrial arginyl-tRNA synthetase gene deficiency: report of two cases and literature review].

Objective: To summarize the clinical features of two early onset epileptic encephalopathy (EOEE) patients with arginyl-tRNA synthetase (RARS2) gene variations and to review related literature. Methods: The clinical data and genetic features of two pontocerebellar hypoplasia type 6 (PCH6) patients with RARS2 variation diagnosed by the Department of Neurology, Beijing Children's Hospital from January 2017 to December 2018 were analyzed retrospectively. A literature search with "RARS2" "pontocerebellar hypoplasia type 6" and "early onset epileptic encephalopathy" as key words was conducted at China national knowledge infrastructure (CNKI), Wanfang Data Knowledge Service Platform and PubMed (up to May 2020), literature about RARS2 gene variation patients and their complete clinical data were chosen and reviewed. Results: The onset age of the two cases (1 male, 1 female) were 2 months and 29 days respectively and the early onset symptom of them was epileptic encephalopathy. The main symptoms included seizures, development delay, microcephaly and lactic acidosis. In addition to these symptoms, the female also had dyspnea, hypoglycemia and metabolic acidosis after birth. Brain magnetic resonance imaging (MRI) of the two patients were normal at first. Follow up at four-month (case 1) and eight-month (case 2) MRI showed atrophy of cerebral and cerebellar, but the pons was not affected. All four heterozygous variations in RARS2 gene revealed by whole-exome sequencing (p.Arg560His and p.Arg6His from case 1, p.Arg254Trp and p.Phe5Ser from case 2) were novel. No eligible reports were found in Chinese journals, while 17 reports were found in English literature. Excluded cases with incomplete data together with these two cases, a total of 34 patients from 20 families were found. All patients had developmental delay while 94% (32/34) patients showed the initial symptoms within 3 months, 93% (28/30) patients were diagnosed as epilepsy, 89% (25/28) patients had progressively microcephaly and 52% (16/31) cases did not show the pons atrophy on brain MRI. Twenty of 28 cases (71%) were refractory epilepsy. There were 31 types of gene variations and most of them were missense variations (21/31, 68%). Conclusions: The majority of PCH6 cases caused by RARS2 gene variation show the initial symptoms within 3 months, characterized by EOEE, most of them are refractory epilepsy, accompanied by developmental delay, microcephaly and increased lactic acid. Brain MRI indicates progressive cerebral or pontocerebellar atrophy.

The Use of FDG PET Parametric Imaging in the Diagnosis of Olivopontocerebellar Atrophy.

Olivopontocerebellar atrophy is a rare neurodegenerative syndrome associated with 2 distinct disorders: multiple system atrophy and spinocerebellar ataxia. We present a case involving a 66-year-old man with adult-onset progressing cerebellar signs reflective of a cerebellar syndrome with no significant family history and unremarkable genetic testing for spinocerebellar ataxia. This case was found to be most consistent with sporadic olivopontocerebellar atrophy, which falls under the multiple system atrophy category. This diagnosis can be made using F-FDG PET/CT scanning and with MRI in some cases. However, in this case, relatively new PET/CT quantification and parametric imaging software was used for analysis, CortexID Suite.

New Radiologic Findings of Hypertrophic Olivary Degeneration in 2 Patients with Brainstem Lymphoma.

BACKGROUND: Hypertrophic olivary degeneration (HOD) is a rare neurological condition of trans-synaptic degeneration caused by disruption of the dentatorubro-olivary pathway. We present new radiologic findings of HOD in 2 cases of brainstem lymphoma. CASE DESCRIPTION: A 35-year-old woman (Case 1) and a 69-year-old man (Case 2) presented with remarkably similar clinical courses. The primary lesion was located at the dorsal pons extending to the midbrain. Pathologic diagnosis of diffuse large B-cell lymphoma was obtained after surgical resection. Complete remission of the primary lesion was achieved by treatment with 3 courses of high-dose methotrexate and radiotherapy. Arterial spin-labeling and T2-weighted imagings showed high signal intensity in the inferior olive (IO) at some time after the operation. Slight contrast enhancement in the IO was also found in Case 1. These radiologic findings nearly misled us into a diagnosis of recurrence of lymphoma. Signal intensity in the IO on arterial spin-labeling imaging changed with time. Normalized regional cerebral blood flow (rCBF) in the IO was defined as a percentage of rCBF to the global cerebral blood flow calculated using automated software. Chronologic change in normalized rCBF in the IO revealed a large peak in Case 1, but only a mild increase in Case 2. Neurological findings demonstrated severe oculopalatal tremor in Case 1 and mild palatal tremor in Case 2. CONCLUSIONS: Hyperperfusion and contrast enhancement in the IO were found in 2 patients with HOD. These findings may be confused with recurrence of malignant tumor.

[Multisemic atrophy: a description of the clinical case of olivopontocerebellar atrophy against the background of stenosing atherosclerotic vascular lesions].

Features of the onset, the course of the disease causes difficulties in the early diagnosis and formulation of the correct diagnosis. Olivopontocerebellar atrophy is characterized by a broad polymorphism of clinical manifestations. There is a need to develop new methods of symptomatic and neuroprotective treatment, as well as the optimization of non-drug therapy.

Unilateral Symptomatic Hypertrophic Olivary Degeneration Secondary to Midline Brainstem Cavernous Angioma: A Case Report and Review of the Literature.

BACKGROUND: Hypertrophic olivary degeneration (HOD) is a rare phenomenon in the dento-rubro-olivary pathway caused by lesion or disruption of the fibers of the Guillain-Mollaret triangle. Hemorrhage of pontine and midbrain cavernous angiomas can rarely lead to HOD portending neurologic deterioration and possible concomitant life-threatening complications; for this reason, it may define a poignant consideration in planning intervention. CASE DESCRIPTION: The patient was a 57-year-old woman with known midbrain-pontine cavernous angioma. For several years, the lesion had been stable, as shown by imaging follow-up, until 10 months before the patient presented with falls, dysarthria, and headache. Imaging showed some decrease in size as well as blood product around the cavernous angioma, suggesting interim period hemorrhage and interval development of HOD. CONCLUSIONS: The literature regarding imaging recommendations for stable cavernous angioma in the midbrain-pontine junction is reviewed. The implication of HOD for patient outcome is discussed and a comment is made on how the development of HOD may affect management of the cavernous angioma.

A New Patient With Intermediate Severe Salla Disease With Hypomyelination: A Literature Review for Salla Disease.

BACKGROUND: Likely pathogenic variants in SLC17A5 results in allelic disorders of free sialic acid metabolism including (1) infantile free sialic acid storage disease with severe global developmental delay, coarse facial features, hepatosplenomegaly, and cardiomegaly; (2) intermediate severe Salla disease with moderate to severe global developmental delay, hypotonia, and hypomyelination with or without coarse facial features, and (3) Salla disease with normal appearance, mild cognitive dysfunction, and spasticity. PATIENT DESCRIPTION: This five-year-old girl presented with infantile-onset severe global developmental delay, truncal hypotonia, and generalized dystonia following normal development during her first six months of life. Brain magnetic resonance imaging showed marked hypomyelination and a thin corpus callosum at age 19 months, both unchanged on follow-up at age 28 months. Urine free sialic acid was moderately elevated. Cerebrospinal fluid free sialic acid was marginally elevated. Sequencing of SLC17A5 revealed compound heterozygous likely pathogenic variants, namely, a known missense (c.291G>A) variant and a novel truncating (c.819+1G>A) variant, confirming the diagnosis of Salla disease at age 3.5 years. CONCLUSION: We report a new patient with intermediate severe Salla disease. Normal or marginally elevated urine or cerebrospinal fluid free sialic acid levels cannot exclude Salla disease. In patients with progressive global developmental delay and hypomyelination on brain magnetic resonance imaging, Salla disease should be included into the differential diagnosis.

Classification, diagnosis and potential mechanisms in pontocerebellar hypoplasia.

Pontocerebellar Hypoplasia (PCH) is group of very rare, inherited progressive neurodegenerative disorders with prenatal onset. Up to now seven different subtypes have been reported (PCH1-7). The incidence of each subtype is unknown. All subtypes share common characteristics, including hypoplasia/atrophy of cerebellum and pons, progressive microcephaly, and variable cerebral involvement. Patients have severe cognitive and motor handicaps and seizures are often reported. Treatment is only symptomatic and prognosis is poor, as most patients die during infancy or childhood. The genetic basis of different subtypes has been elucidated, which makes prenatal testing possible in families with mutations. Mutations in three tRNA splicing endonuclease subunit genes were found to be responsible for PCH2, PCH4 and PCH5. Mutations in the nuclear encoded mitochondrial arginyl- tRNA synthetase gene underlie PCH6. The tRNA splicing endonuclease, the mitochondrial arginyl- tRNA synthetase and the vaccinia related kinase1 are mutated in the minority of PCH1 cases. These genes are involved in essential processes in protein synthesis in general and tRNA processing in particular. In this review we describe the neuroradiological, neuropathological, clinical and genetic features of the different PCH subtypes and we report on in vitro and in vivo studies on the tRNA splicing endonuclease and mitochondrial arginyl-tRNA synthetase and discuss their relation to pontocerebellar hypoplasia.

Topographic brain mapping of the international cooperative ataxia rating scale. A positron emission tomography study.

The International Cooperative Ataxia Rating Scale (ICARS) is a 100-point semiquantitative scale designed primarily to assess cerebellar dysfunction. However, little is known of the metric properties of this scale. We assessed the ICARS by rating the severity of cerebellar dysfunction in 27 patients with spinocerebellar ataxias (SCA), three patients with sporadic olivopontocerebellar ataxia and 24 healthy control subjects. [(18)F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) study was also performed on each subject. The statistical parametric mapping analyses revealed a significant correlation between the ICARS scores and functional impairment of the frontal regions within SCA patients. The glucose metabolism in the cerebellum, thalamus and caudate nucleus had significant differences between SCA patients and healthy control subjects. The results suggested that the clinical severity of SCA patients correlated with the functional impairment in the frontal regions, the targets of cerebellar efferent projections.

Severe form of congenital cerebral and cerebellar atrophy: a neurodegenerative disorder of fetal onset.

Infantile olivopontocerebellar atrophy (OPCA) is a rare congenital disorder likely due to an intrauterine neurodegenerative condition. Characteristic presentations are failure to thrive, cerebellar ataxia, respiratory insufficiency, and hypotonia or hypertonia. A few cases with severe manifestations (eg, the Pena-Shokeir phenotype) presenting in the neonatal period have also been reported. We present a case of infantile OPCA with the Pena-Shokeir II phenotype and severe atrophy of the cerebellum and cerebral hemispheres. Comparison of prenatal sonographic findings of the fetal brain at 30 weeks' menstrual age and CT findings during the neonatal period indicated prenatal onset of the neurodegenerative process, which progressed rapidly during the last trimester.

[Analysis of brain images in patients with spinocerebellar degeneration; using statistical parametric mapping (SPM) and easy Z score imaging system (eZIS)].

In order to investigate the cerebral blood flow objectively, the easy Z score imaging system (eZIS), was developed, and has been applied in clinical practice. SPECT with 99mTc-ethyl cysteinate dimer (99mTc-ECD) was performed, and the images were analyzed using the SPM97 and the eZIS Ver. 2 to investigate cerebral blood flow in patients with two types of spino-cerebellar degeneration. We compared the distribution of cerebral blood flow between 13 patients with cortical cerebellar atrophy (CCA) and 26 patients with olivopontocerebellar atrophy (OPCA). In the both groups, cerebellar blood flow was decreased generally. In our evaluation using the eZIS Z score, the scores for the brain stem and cerebellar nucleus in the OPCA group were lower than those in the CCA group. This method facilitates the objective evaluation of cerebral blood flow in patients with spinocerebellar degeneration, and may be useful for analyzing the condition of these disease.

[Application of rCBF imaging in PD, AD and OPCA].

OBJECTIVE: To evaluate the diagnosis and differential diagnosis of rCBF imaging in Parkison's disease (PD), Alzheimer's disease (AD) and olivopontocerebellar atrophy (OPCA). METHODS: The characteristics of the radioactive distribution of rCBF imaging in PD, AD and OPCA were analyzed, and the laws of the radioactive distribution were identified. RESULTS: The sensitivity of rCBF imaging in PD, AD and OPCA was 88.4% (38/43), 95.8% (23/24), and 85.7% (30/35) respectively. The characteristics of the radioactive distribution were that the radioactivity decreased in the cerebral cortex (25/43), basal nuclei (21/43) and thalamus (18/43) in PD, that the radioactivity decreased in the bilateral cerebral cortex (17/24) in AD, that the radioactivity decreased in the cerebral cortex (17/35), cerebellum (14/35), basal nuclei (14/35) and thalamus (10/35) in OPCA. CONCLUSION: rCBF imaging could sensitively diagnose PD, AD and OPCA, and also could differentially diagnose them according to their different characteristics of the radioactive distribution.

Preclinical impairment of the striatal dopamine transporter system in sporadic olivopontocerebellar atrophy: studied with [(123)I]beta-CIT and SPECT.

We investigated whether the dopamine (DA) transporter system is impaired in sporadic olivopontocerebellar atrophy (sOPCA) patients without clinical parkinsonism using the DA transporter radiotracer [(123)I]beta-CIT [2beta-carboxymethoxy-3beta-(4-iodophenyl)tropane] and single-photon emission computed tomography (SPECT). SPECT scans were acquired in 9 patients with sOPCA, 7 multiple system atrophy (MSA) patients with parkinsonism (MSA-P), and 7 age-matched healthy controls 20-24 h after the intravenous injection of [(123)I]beta-CIT. [(123)I]beta-CIT-specific binding in the striatum was determined as the radioactivity ratio of the striatum to the occipital cortex (specific binding ratio, SBR). In patients with sOPCA and MSA-P, SBRs in the right and left striatum and the mean SBR were significantly lower than those in controls (p < 0.05). The mean SBRs in patients with sOPCA and MSA-P were reduced to 69.0 and 60.7% of the control mean, respectively. However, there was no significant difference in SBRs between sOPCA and MSA-P patients. In sOPCA patients, the mean SBR was significantly correlated with the score of the clinical cerebellar function scale (r = -0.670, p = 0.024). These results indicate that even in the absence of clinical parkinsonism, the striatal dopaminergic system may be impaired in sOPCA. The DA transporter loss in sOPCA serves as another clue for sOPCA being a part of the spectrum of MSA.

Cerebellar activation during ataxic gait in olivopontocerebellar atrophy: a PET study.

OBJECTIVE: To investigate the possible abnormal regional brain metabolism during ataxic gait in olivopontocerebellar atrophy (OPCA), and to evaluate the response of the cerebellar subregions to instability during bipedal gait. MATERIAL AND METHODS: On 9 patients with OPCA in early phase and on 10 age-matched normal subjects, we performed positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose (FDG) under two different conditions: supine resting and 30 min treadmill walking. RESULTS: Both in normals and in patients with OPCA, the FDG uptake in the walking state (Uwalk) was significantly greater than that in the resting state (Urest) in the pyramis, declive-folium-tuber and culmen of the cerebellar vermis, and in the thalamus. In the patients, the Uwalk was also significantly greater than the Urest in the posterior lobe of cerebellar hemisphere and in the pons and midbrain. In the pyramis, the activation ratio (= Uwalk/Urest) of the patients was significantly lower than that of the normals. CONCLUSIONS: We considered that these findings reflect the pathophysiology of ataxic gait in OPCA patients and the compensatory mechanism for the instability during ataxic gait.

Prenatal diagnosis of fatal infantile olivopontocerebellar hypoplasia syndrome.

We report the first case of prenatal diagnosis of fatal infantile olivopontocerebellar hypoplasia syndrome, OMIM 225753. Ultrasound findings noted at 28 weeks' gestation included polyhydramnios, a small stomach bubble, a small but morphologically normal cerebellum, dilatation of the fourth ventricle, and long periods of normal fetal movement punctuated by sudden bursts of violent seizure-like activity of the fetal extremities. At birth, the child was noted to be hypertonic, myoclonic, hyper-reflexic, demonstrated poor gastrointestinal motility, and had severe apneic episodes. Magnetic resonance imaging (MRI) demonstrated marked hypoplasia or atrophy of the cerebellum, pons and medulla, mild atrophy of the cerebral cortex, and mild ex vacuo venticulomegaly of the fourth, third and lateral ventricles. This child died from respiratory insufficiency at 14 days of age. The parents of this child had previously lost a child with similar clinical and anatomical findings. Prenatal sonographers should be aware of the existence of this rare syndrome and should look carefully at the size of the cerebellum in cases of polyhydramnios or when in utero 'seizure-like' activity is seen. The importance of establishing this diagnosis lies in the fact that it appears to have a very poor postnatal prognosis and is likely to be inherited as an autosomal recessive disease.