Clinical and Molecular Characteristics of Neuronal Ceroid Lipofuscinosis in Saudi Arabia

BACKGROUND

Neuronal ceroid lipofuscinoses (NCLs) represent a heterogeneous group of inherited metabolic lysosomal disorders characterized by neurodegeneration. This study sought to describe the clinical and molecular characteristics of NCLs in Saudi Arabia and determine the most common types in that population.

METHODS

A retrospective review of electronic medical records was conducted for 63 patients with NCL (55 families) from six tertiary and referral centers in Saudi Arabia between 2008 and 2022. Clinical, radiological, and neurophysiological data as well as genetic diagnoses were reviewed.

RESULTS

CLN6 was the predominant type, accounting for 45% of cases in 25 families. The most common initial symptoms were speech delay (53%), cognitive decline (50%) and/or gait abnormalities (48%), and seizure (40%). Behavioral symptomatology was observed in 20%, whereas visual impairment was less frequently (9.3%) encountered. Diffuse cerebral and cerebellar atrophy was the predominant finding on brain magnetic resonance imaging. Electroencephalography generally revealed background slowing in all patients with generalized epileptiform discharges in 60%. The most common genotype detected was the p.Ser265del variant found in 36% (20 of 55 families). The most rapidly progressive subtypes were CLN2 and CLN6. Two patients with each died at age five years. The earliest age at which a patient was nonambulatory was two years in a patient with CLN14.

CONCLUSIONS

This is the largest molecularly confirmed NCL cohort study from Saudi Arabia. Characterizing the natural history of specific NLC types can increase understanding of the underlying pathophysiology and distinctive genotype-phenotype characteristics, facilitating early diagnosis and treatment initiation as well as genetic counseling for families.

Case Report: A rare treatable metabolic syndrome (Brown-Vialetto-Van Laere syndrome) masquerading as chronic inflammatory demyelinating polyneuropathy from Saudi Arabia

Background

Brown-Vialetto-Van Laere (BVVL) syndrome is an extremely rare autosomal recessive progressive motoneuron disease that is caused by a defect in the riboflavin transporter genes SLC52A2 and SLC52A3. BVVL syndrome has a variable age of presentation, and it is characterized by progressive auditory neuropathy, bulbar palsy, stridor, muscle weakness, and respiratory compromise secondary to diaphragmatic and vocal cord paralysis. BVVL syndrome has a poor prognosis in the absence of treatment, including morbidity with quadriparesis and sensorineural hearing loss, with mortality in the younger age group. Early administration of riboflavin is associated with prolonged survival, low morbidity, and reversal of some clinical manifestations.

Case presentation

We describe an 18-month-old male infant with progressive pontobulbar palsy, loss of developmental milestones, and a clinical picture suggestive of chronic inflammatory demyelinating neuropathy. A nerve conduction study revealed axonal neuropathy, while molecular analysis revealed a homozygous mutation in one of the riboflavin transporter genes, SLC52A3, confirming BVVL syndrome. The patient needed long-term respiratory support and a gastrostomy tube to support feeding. With high-dose riboflavin supplementation, he experienced moderate recovery of motor function.

Conclusion

This report highlights the importance of considering BVVL syndrome in any patient who presents with the clinical phenotype of pontobulbar palsy and peripheral axonal neuropathy, as early riboflavin treatment may improve or halt disease progression, thus reducing the associated mortality and morbidity.

SHQ1-associated neurodevelopmental disorder: Report of the first homozygous variant in unrelated patients and review of the literature

Compound heterozygous mutations in SHQ1 have been associated with a rare and severe neurological disorder characterized by global developmental delay (GDD), cerebellar degeneration coupled with seizures, and early-onset dystonia. Currently, only five affected individuals have been documented in the literature. Here, we report three children from two unrelated families harboring a homozygous variant in the gene but with a milder phenotype than previously described. The patients had GDD and seizures. Magnetic resonance imaging analyses revealed diffuse white matter hypomyelination. Sanger sequencing confirmed the whole-exome sequencing results and revealed full segregation of the missense variant (SHQ1:c.833 T > C; p.I278T) in both families. We performed a comprehensive in silico analysis using different prediction classifiers and structural modeling of the variant. Our findings demonstrate that this novel homozygous variant in SHQ1 is likely to be pathogenic and leads to the clinical features observed in our patients.

Efficacy and safety of corpus callosotomy versus vagus nerve stimulation as long-term adjunctive therapies in children with Lennox–Gastaut syndrome

Objectives:

To compare the efficacy and safety of corpus callosotomy versus vagus nerve stimulation (VNS) as long-term adjunctive therapies in children with Lennox–Gastaut syndrome.

Methods:

This retrospective study was conducted in King Fahad Medical City between 2010 and 2019. The authors identified and followed 9 patients with Lennox–Gastaut syndrome (LGS) who underwent corpus callosotomy or VNS implantation for at least 12 months; seizure frequency and major complications were monitored. Five patients with a mean age of 10.8±1.3 years had corpus callosotomy, and 4 patients with a mean age of 13.8±3.9 years were implanted with VNS stimulators.

Results:

Reduction in seizure frequency was achieved in all 5 patients who underwent corpus callosotomy, with greater than 75% seizure reduction in more than 50% in one, and greater than 25% in 2 respectively. However, in those implanted with VNS, 2 (50%) patients achieved a reduction in seizure frequency of greater than 75% and 2 (50%) greater than 25%, respectively. No significant difference was observed between the 2 treatment groups. One patient who underwent corpus callosotomy suffered cerebrospinal fluid leakage, and swallowing difficulties in one patient who underwent VNS.

Conclusion:

Both corpus callosotomy and VNS are safe and effective as adjunctive treatments for LGS patients.

Clinico-radiological features, molecular spectrum, and identification of prognostic factors in developmental and epileptic encephalopathy due to inosine triphosphate pyrophosphatase (ITPase) deficiency

Developmental and epileptic encephalopathy 35 (DEE 35) is a severe neurological condition caused by biallelic variants in ITPA, encoding inosine triphosphate pyrophosphatase, an essential enzyme in purine metabolism. We delineate the genotypic and phenotypic spectrum of DEE 35, analyzing possible predictors for adverse clinical outcomes. We investigated a cohort of 28 new patients and reviewed previously described cases, providing a comprehensive characterization of 40 subjects. Exome sequencing was performed to identify underlying ITPA pathogenic variants. Brain MRI (magnetic resonance imaging) scans were systematically analyzed to delineate the neuroradiological spectrum. Survival curves according to the Kaplan-Meier method and log-rank test were used to investigate outcome predictors in different subgroups of patients. We identified 18 distinct ITPA pathogenic variants, including 14 novel variants, and two deletions. All subjects showed profound developmental delay, microcephaly, and refractory epilepsy followed by neurodevelopmental regression. Brain MRI revision revealed a recurrent pattern of delayed myelination and restricted diffusion of early myelinating structures. Congenital microcephaly and cardiac involvement were statistically significant novel clinical predictors of adverse outcomes. We refined the molecular, clinical, and neuroradiological characterization of ITPase deficiency, and identified new clinical predictors which may have a potentially important impact on diagnosis, counseling, and follow-up of affected individuals.

Clinical, molecular, and biochemical delineation of asparagine synthetase deficiency in Saudi cohort

PURPOSE

Asparagine synthetase deficiency (ASNSD) is a rare neurometabolic disease. Patients may not demonstrate low asparagine levels, which highlights the advantage of molecular over biochemical testing in the initial work-up of ASNSD. We aimed to further delineate the ASNSD variant and phenotypic spectrum and determine the value of biochemical testing as a frontline investigation in ASNSD.

METHODS

We retrospectively collected the clinical and molecular information on 13 families with ASNSD from the major metabolic clinics in Saudi Arabia.

RESULTS

The major phenotypes included congenital microcephaly (100%), facial dysmorphism (100%), global developmental delay (100%), brain abnormalities (100%), spasticity (86%), and infantile-onset seizures (93%). Additional unreported phenotypes included umbilical hernia, osteopenia, eczema, lung hypoplasia, and hearing loss. Overall, seven homozygous variants accounted for ASNSD. The p.Tyr398Cys and p.Asn75Ile variants accounted for 54% of the cases. The clinical sensitivity and specificity of the proposed biochemical analysis of cerebrospinal fluid (CSF) for the detection of patients with ASNSD were 83% and 98%, respectively.

CONCLUSION

Our study describes the largest reported ASNSD cohort with clinical, molecular, and biochemical characterization. Taking into consideration the suboptimal sensitivity of biochemical screening, the delineation of the phenotype variant spectrum is of diagnostic utility for accurate diagnosis, prognosis, counseling, and carrier screening.

Predicting future handedness and hemispheric dominance during infancy by analyzing sleep spindles

OBJECTIVE

To investigate whether sleep spindles asynchrony (SSA) using scalp sleep electroencephalogram (EEG) among children below 2 years of age can predict future handedness.

METHODS

This is a retrospective study conducted from October 2016 until June 2017 at the King Fahad Medical City (KFMC), Riyadh, Kingdom of Saudi Arabia. We retrospectively reviewed 300 EEGs recorded at our neurophysiology laboratory.We included EEGs performed during sleep for infants aged 2 months to 2 years who have already attained their handedness or those aged above 2 years. We excluded records of children younger than 2 months or above 2 years of age (at the time of the EEG) or those aged below 2 years (at the time of the interview), and severely abnormal tracings and those without sleep or enough SSA.

RESULTS

The lateralization of Sleep Spindles (SS) was mostly right-hemispheric (52%) compared to left-hemispheric (36.4%). The overall SS laterality did not correlate with handedness (p=0.81). In the majority of right-handed (64%) and left-handed (60%) children, the SSA was contralateral to the side of hand preference; however, it did not correlate statistically (p=0.377).

CONCLUSION

We were unable to prove a statistically significant correlation between SSA and future hand preference. Further research involving larger cohorts is still needed.

Pediatric intracranial hypertension. Experience from 2 Tertiary Centers

OBJECTIVE

To review the experience of 2 tertiary centers in Saudi Arabia with intracranial hypertension (IH) in the pediatric population.

METHODS

We retrospectively reviewed and analyzed pediatric patients diagnosed with IH from June 2002 to May 2017 in 2 institutes.

RESULTS

We identified 53 patients (30 females and 23 males) with a mean age of 7 years at the time of presentation. Among them, 41 patients were younger than 12 years, and 12 were older. Obese and overweight patients constituted 27.00% (n = 14) of all cases, 8 (66.7%) of whom were older than 12 years. The most common presenting feature was papilledema followed by headache. Vitamin D deficiency, which constituted the most common associated condition, was identified in 12 (22.6%) patients. Acetazolamide was the treatment option in 98.11% of patients, and only 5.7% underwent surgical interventions. The length of follow-up ranged from 6 months to 8 years.

CONCLUSION

Intracranial hypertension is rare in children and commonly seen in overweight females older than 12 years similar to adults. Patients younger than 12 years tend to develop secondary IH. More studies are needed to characterize the clinical presentation and guide the management plan.

Acute Necrotizing Encephalopathy of Childhood: A Multicenter Experience in Saudi Arabia

Background: Acute necrotizing encephalopathy of childhood (ANEC) is a rapidly progressing encephalopathy characterized by fever, depressed level of consciousness, and seizures. Diagnosis depends on clinical presentation and characteristic neuroimaging findings of abnormal signal intensity involving the thalami as well as the supra and infra-tentorial areas. Treatment modalities are not well-established; empirical treatment with antibiotics and antiviral agents is the initial step, followed by steroids and immunoglobulin, as well as supportive care. Patients with ANEC have a variable prognosis, but mortality is very high. Methods: A retrospective chart review of patients diagnosed with ANEC in five tertiary centers from January 2015 to October 2018 was performed. Clinical and radiological findings, as well as the therapeutic approach and outcomes, were described. Results: Twelve children were included ranging in age from 10 months to 6 years. All patients presented with preceding febrile illness, altered level of consciousness, and seizure. Radiological features showed abnormal signals in the thalami, and five patients (41.7%) had brainstem involvement. All patients received empirical treatment with antibiotics and antiviral agents. Ten patients (83.3%) received intravenous immunoglobulin (IVIG) and IV Methylprednisolone therapy. Outcomes were variable ranging from good outcomes with minimal neurological deficits to poor outcomes and death in 25% of cases. Conclusion: ANEC is a rare fulminant disease in children. The treatment is challenging. Early interventions with the use of IVIG and IV Methylprednisolone may change the outcome; however, further studies are needed to establish a consensus guideline for the management.

Management of convulsive status epilepticus in children: an adapted clinical practice guideline for pediatricians in Saudi Arabia

Objective:

To increase the use of evidence-based approaches in the diagnosis, investigations and treatment of Convulsive Status Epilepticus (CSE) in children in relevant care settings.

Method:

A Clinical Practice Guideline (CPG) adaptation group was formulated at a university hospital in Riyadh. The group utilized 2 CPG validated tools including the ADAPTE method and the AGREE II instrument.

Results:

The group adapted 3 main categories of recommendations from one Source CPG. The recommendations cover; (i)first-line treatment of CSE in the community; (ii)treatment of CSE in the hospital; and (iii)refractory CSE. Implementation tools were built to enhance knowledge translation of these recommendations including a clinical algorithm, audit criteria, and a computerized provider order entry.

Conclusion:

A clinical practice guideline for the Saudi healthcare context was formulated using a guideline adaptation process to support relevant clinicians managing CSE in children.

Genomic and phenotypic delineation of congenital microcephaly

PURPOSE

Congenital microcephaly (CM) is an important birth defect with long term neurological sequelae. We aimed to perform detailed phenotypic and genomic analysis of patients with Mendelian forms of CM.

METHODS

Clinical phenotyping, targeted or exome sequencing, and autozygome analysis.

RESULTS

We describe 150 patients (104 families) with 56 Mendelian forms of CM. Our data show little overlap with the genetic causes of postnatal microcephaly. We also show that a broad definition of primary microcephaly -as an autosomal recessive form of nonsyndromic CM with severe postnatal deceleration of occipitofrontal circumference-is highly sensitive but has a limited specificity. In addition, we expand the overlap between primary microcephaly and microcephalic primordial dwarfism both clinically (short stature in >52% of patients with primary microcephaly) and molecularly (e.g., we report the first instance of CEP135-related microcephalic primordial dwarfism). We expand the allelic and locus heterogeneity of CM by reporting 37 novel likely disease-causing variants in 27 disease genes, confirming the candidacy of ANKLE2, YARS, FRMD4A, and THG1L, and proposing the candidacy of BPTF, MAP1B, CCNH, and PPFIBP1.

CONCLUSION

Our study refines the phenotype of CM, expands its genetics heterogeneity, and informs the workup of children born with this developmental brain defect.

FARS2 deficiency; new cases, review of clinical, biochemical, and molecular spectra, and variants interpretation based on structural, functional, and evolutionary significance

An increasing number of mitochondrial diseases are found to be caused by pathogenic variants in nuclear encoded mitochondrial aminoacyl-tRNA synthetases. FARS2 encodes mitochondrial phenylalanyl-tRNA synthetase (mtPheRS) which transfers phenylalanine to its cognate tRNA in mitochondria. Since the first case was reported in 2012, a total of 21 subjects with FARS2 deficiency have been reported to date with a spectrum of disease severity that falls between two phenotypes; early onset epileptic encephalopathy and a less severe phenotype characterized by spastic paraplegia. In this report, we present an additional 15 individuals from 12 families who are mostly Arabs homozygous for the pathogenic variant Y144C, which is associated with the more severe early onset phenotype. The total number of unique pathogenic FARS2 variants known to date is 21 including three different partial gene deletions reported in four individuals. Except for the large deletions, all variants but two (one in-frame deletion of one amino acid and one splice-site variant) are missense. All large deletions and the single splice-site variant are in trans with a missense variant. This suggests that complete loss of function may be incompatible with life. In this report, we also review structural, functional, and evolutionary significance of select FARS2 pathogenic variants reported here.

Loss-of-function mutation in RUSC2 causes intellectual disability and secondary microcephaly

Inherited aberrancies in intracellular vesicular transport are associated with a variety of neurological and non-neurological diseases. RUSC2 is a gene found on chromosome 9p13.3 that codes for iporin, a ubiquitous protein with high expression in the brain that interacts with Rab proteins (GTPases implicated in intracellular protein trafficking). Although mutations in Rab proteins have been described as causing brain abnormalities and intellectual disability, until now no disease-causing mutations in RUSC2 have ever been reported in humans. We describe, to our knowledge for the first time, three patients with inherited homozygous nonsense mutations identified in RUSC2 on whole-exome sequencing. All three patients had central hypotonia, microcephaly, and moderate to severe intellectual disability. Two patients had additional features of early-onset epilepsy and absence of the splenium. This report adds to the ever-expanding landscape of genetic causes of intellectual disability and increases our understanding of the cellular processes underlying this important neurological entity.

Idiopathic intracranial hypertension in children: Diagnostic and management approach

Idiopathic intracranial hypertension (IIH) is a rare neurological disorder in children. It is characterized by raised intracranial pressure (ICP) in the absence of brain parenchymal lesion, vascular malformations, hydrocephalus, or central nervous system (CNS) infection. The diagnosis is usually confirmed by high opening pressure of cerebrospinal fluid (CSF) with exclusion of secondary causes of intracranial hypertension. If not treated properly, it may lead to severe visual dysfunction. Here we review the etiology, clinical presentation, diagnostic criteria and management of IIH in children through illustration of the clinical and radiological presentation of a 13-year-old overweight girl who presented with severe headache, diplopia and bilateral papilledema. Otherwise, she had unremarkable neurological and systemic examinations. Lumbar puncture showed a high CSF opening pressure (360-540 mmH2O). Her investigations showed normal complete blood count (CBC), normal renal, liver, and thyroid function tests. Cerebrospinal fluid (CSF) and blood chemistry were unremarkable. Magnetic resonant image (MRI) of the brain demonstrated empty sella turcica, tortuous optic nerves, and flattening of the posterior sclera. Magnetic resonant venography (MRV) showed focal narrowing of the distal transverse sinuses and absence of venous sinus thrombosis. She required treatment with acetazolamide and prednisolone. With medical treatment, weight reduction, and exercise, our patient had a remarkable improvement in her symptoms with resolution of papilledema in two months. This review highlights the importance of early recognition and management of IIH to prevent permanent visual loss.