Genome sequencing reanalysis increases the diagnostic yield in dystonia

PURPOSE

We investigated the contribution of genomic data reanalysis to the diagnostic yield of dystonia patients who remained undiagnosed after prior genome sequencing.

METHODS

Probands with heterogeneous dystonia phenotypes who underwent initial genome sequencing (GS) analysis in 2019 were included in the reanalysis, which was performed through gene-specific discovery collaborations and systematic genomic data reanalysis.

RESULTS

Initial GS analysis in 2019 (n = 111) identified a molecular diagnosis in 11.7 % (13/111) of cases. Reanalysis between 2020 and 2023 increased the diagnostic yield by 7.2 % (8/111); 3.6 % (4/111) through focused gene-specific clinical correlation collaborative efforts [VPS16 (two probands), AOPEP and POLG], and 3.6 % (4/111) by systematic reanalysis completed in 2023 [NUS1 (two probands) and DDX3X variants, and a microdeletion encompassing VPS16]. Seven of these patients had a high phenotype-based dystonia score ≥3. Notable unverified findings in four additional cases included suspicious variants of uncertain significance in FBXL4 and EIF2AK2, and potential phenotypic expansion associated with SLC2A1 and TREX1 variants.

CONCLUSION

GS data reanalysis increased the diagnostic yield from 11.7 % to 18.9 %, with potential extension up to 22.5 %. While optimal timing for diagnostic reanalysis remains to be determined, this study demonstrates that periodic re-interrogation of dystonia GS datasets can provide additional genetic diagnoses, which may have significant implications for patients and their families.

A single centre prospective study of three device-assisted therapies for Parkinson's disease

Comparative studies assessing outcomes with the three device-assisted therapies could help to individualise treatment for patients living with Parkinson's disease. We designed a single-centre non-randomised prospective observational study assessing the quality of life (QoL), motor and non-motor outcomes at 6 and 12-months in patients treated with subcutaneous apomorphine continuous 16-hours infusion (APO), levodopa-carbidopa intestinal gel (LCIG) or subthalamic nucleus deep brain stimulation (STN-DBS). In this study, 66 patients were included (13 APO; 19 LCIG; 34 STN-DBS). At baseline, cognitive, non-motor and motor scores were significantly less severe in the STN-DBS group, whereas the LCIG group had a longer disease duration and higher non-motor scores. In the APO group, there were no statistically significant changes in non-motor, motor and QoL scales. The LCIG group had significant changes in QoL and motor scales that were significant after multiple comparison analysis at 6 and 12-months. The STN-DBS group showed improvement in QoL scores and non-motor and motor scores at 6 and 12-months after multiple comparison analysis. In this real-life prospective study, device-assisted therapies showed differences in their effects on QoL and motor and non-motor function at 12-months. However, there were also differences in baseline characteristics of the patient groups that were not based on pre-determined selection criteria. Differences in characteristics of patients offered and/or treatment with different device-assisted therapies may reflect within-centre biases that may, in turn, influence perceptions of treatment efficacy or outcomes. Treatment centres should be aware of this potential confounder when assessing and offering device-assisted treatment options to their patients and potential baseline differences need to be taken into consideration when comparing the results of non-randomised studies.

The initial diagnosis and management of Parkinson's disease

BACKGROUND

Parkinson's disease is a common, progressive neurodegenerative disorder, the prevalence of which is on the rise. The diagnosis and management of Parkinson's disease is therefore likely to become increasingly frequent in general practice.

OBJECTIVE

The aim of this article is to provide a practical overview for the general practitioner of the initial diagnosis and management of Parkinson's disease.

DISCUSSION

Parkinson's disease is a multisystem disorder, and the way the diagnosis is delivered, as well as the early management, can have a lasting impact on the patient experience. In this article, the authors present their preferred approach to diagnosis and initial treatment, while highlighting common pitfalls and some useful simple strategies for communicating the diagnosis.

Magnetic resonance imaging pattern recognition in childhood bilateral basal ganglia disorders

Bilateral basal ganglia abnormalities on MRI are observed in a wide variety of childhood disorders. MRI pattern recognition can enable rationalization of investigations and also complement clinical and molecular findings, particularly confirming genomic findings and also enabling new gene discovery. A pattern recognition approach in children with bilateral basal ganglia abnormalities on brain MRI was undertaken in this international multicentre cohort study. Three hundred and five MRI scans belonging to 201 children with 34 different disorders were rated using a standard radiological scoring proforma. In addition, literature review on MRI patterns was undertaken in these 34 disorders and 59 additional disorders reported with bilateral basal ganglia MRI abnormalities. Cluster analysis on first MRI findings from the study cohort grouped them into four clusters: Cluster 1—T₂-weighted hyperintensities in the putamen; Cluster 2—T₂-weighted hyperintensities or increased MRI susceptibility in the globus pallidus; Cluster 3—T₂-weighted hyperintensities in the globus pallidus, brainstem and cerebellum with diffusion restriction; Cluster 4—T₁-weighted hyperintensities in the basal ganglia. The 34 diagnostic categories included in this study showed dominant clustering in one of the above four clusters. Inflammatory disorders grouped together in Cluster 1. Mitochondrial and other neurometabolic disorders were distributed across clusters 1, 2 and 3, according to lesions dominantly affecting the striatum (Cluster 1: glutaric aciduria type 1, propionic acidaemia, 3-methylglutaconic aciduria with deafness, encephalopathy and Leigh-like syndrome and thiamine responsive basal ganglia disease associated with SLC19A3), pallidum (Cluster 2: methylmalonic acidaemia, Kearns Sayre syndrome, pyruvate dehydrogenase complex deficiency and succinic semialdehyde dehydrogenase deficiency) or pallidum, brainstem and cerebellum (Cluster 3: vigabatrin toxicity, Krabbe disease). The Cluster 4 pattern was exemplified by distinct T₁-weighted hyperintensities in the basal ganglia and other brain regions in genetically determined hypermanganesemia due to SLC39A14 and SLC30A10. Within the clusters, distinctive basal ganglia MRI patterns were noted in acquired disorders such as cerebral palsy due to hypoxic ischaemic encephalopathy in full-term babies, kernicterus and vigabatrin toxicity and in rare genetic disorders such as 3-methylglutaconic aciduria with deafness, encephalopathy and Leigh-like syndrome, thiamine responsive basal ganglia disease, pantothenate kinase-associated neurodegeneration, TUBB4A and hypermanganesemia. Integrated findings from the study cohort and literature review were used to propose a diagnostic algorithm to approach bilateral basal ganglia abnormalities on MRI. After integrating clinical summaries and MRI findings from the literature review, we developed a prototypic decision-making electronic tool to be tested using further cohorts and clinical practice.

The Head Retraction Reflex in Niemann-Pick Type C: A Novel Diagnostic Clue

Background

The head retraction reflex (HRR) is characterized by the extension of the neck after percussion stimulation of the central facial region. It is either absent or habituates in normal individuals and can become exaggerated and persistent in certain pathological conditions, having been most commonly reported in hyperekplexia and stiff-person syndrome disorders. It has not, however, been reported in Niemann-Pick type C (NPC), a lipid storage disorder with a variety of neurologic and systemic manifestations. The diagnosis of NPC is often delayed because of the rarity of the condition and the subtlety of clinical signs.

Cases

We present 3 consecutive cases of genetically confirmed NPC with a pathological HRR, which was not present in controls. Neurophysiological analysis showed findings suggestive of myoclonus of brainstem origin.

Conclusion

We propose that the presence of a pathological HRR, an easily performed clinical test, may provide a clue to the diagnosis of NPC.

Clinical and neuroimaging phenotypes of genetic parkinsonism from infancy to adolescence

Genetic early-onset parkinsonism presenting from infancy to adolescence (≤21 years old) is a clinically diverse syndrome often combined with other hyperkinetic movement disorders, neurological and imaging abnormalities. The syndrome is genetically heterogeneous, with many causative genes already known. With the increased use of next-generation sequencing in clinical practice, there have been novel and unexpected insights into phenotype-genotype correlations and the discovery of new disease-causing genes. It is now recognized that mutations in a single gene can give rise to a broad phenotypic spectrum and that, conversely different genetic disorders can manifest with a similar phenotype. Accurate phenotypic characterization remains an essential step in interpreting genetic findings in undiagnosed patients. However, in the past decade, there has been a marked expansion in knowledge about the number of both disease-causing genes and phenotypic spectrum of early-onset cases. Detailed knowledge of genetic disorders and their clinical expression is required for rational planning of genetic and molecular testing, as well as correct interpretation of next-generation sequencing results. In this review we examine the relevant literature of genetic parkinsonism with ≤21 years onset, extracting data on associated movement disorders as well as other neurological and imaging features, to delineate syndromic patterns associated with early-onset parkinsonism. Excluding PRKN (parkin) mutations, >90% of the presenting phenotypes have a complex or atypical presentation, with dystonia, abnormal cognition, pyramidal signs, neuropsychiatric disorders, abnormal imaging and abnormal eye movements being the most common features. Furthermore, several imaging features and extraneurological manifestations are relatively specific for certain disorders and are important diagnostic clues. From the currently available literature, the most commonly implicated causes of early-onset parkinsonism have been elucidated but diagnosis is still challenging in many cases. Mutations in ∼70 different genes have been associated with early-onset parkinsonism or may feature parkinsonism as part of their phenotypic spectrum. Most of the cases are caused by recessively inherited mutations, followed by dominant and X-linked mutations, and rarely by mitochondrially inherited mutations. In infantile-onset parkinsonism, the phenotype of hypokinetic-rigid syndrome is most commonly caused by disorders of monoamine synthesis. In childhood and juvenile-onset cases, common genotypes include PRKN, HTT, ATP13A2, ATP1A3, FBX07, PINK1 and PLA2G6 mutations. Moreover, Wilson’s disease and mutations in the manganese transporter are potentially treatable conditions and should always be considered in the differential diagnosis in any patient with early-onset parkinsonism.

Whole genome sequencing for the genetic diagnosis of heterogenous dystonia phenotypes

INTRODUCTION

Dystonia is a clinically and genetically heterogeneous disorder and a genetic cause is often difficult to elucidate. This is the first study to use whole genome sequencing (WGS) to investigate dystonia in a large sample of affected individuals.

METHODS

WGS was performed on 111 probands with heterogenous dystonia phenotypes. We performed analysis for coding and non-coding variants, copy number variants (CNVs), and structural variants (SVs). We assessed for an association between dystonia and 10 known dystonia risk variants.

RESULTS

A genetic diagnosis was obtained for 11.7% (13/111) of individuals. We found that a genetic diagnosis was more likely in those with an earlier age at onset, younger age at testing, and a combined dystonia phenotype. We identified pathogenic/likely-pathogenic variants in ADCY5 (n = 1), ATM (n = 1), GNAL (n = 2), GLB1 (n = 1), KMT2B (n = 2), PRKN (n = 2), PRRT2 (n = 1), SGCE (n = 2), and THAP1 (n = 1). CNVs were detected in 3 individuals. We found an association between the known risk variant ARSG rs11655081 and dystonia (p = 0.003).

CONCLUSION

A genetic diagnosis was found in 11.7% of individuals with dystonia. The diagnostic yield was higher in those with an earlier age of onset, younger age at testing, and a combined dystonia phenotype. WGS may be particularly relevant for dystonia given that it allows for the detection of CNVs, which accounted for 23% of the genetically diagnosed cases.

Tremor

Tremor is a phenomenon observed in a broad spectrum of diseases with different pathophysiologies. While patients with tremor may not complain in the clinic of symptoms of imbalance, gait difficulties, or falls, laboratory research studies using quantitative analysis of gait and posture and neurophysiologic techniques have demonstrated impaired gait and balance across a variety of tremor etiologies. These findings have been supported by careful epidemiologic studies assessing symptoms of imbalance. Imaging and neurophysiologic studies have identified cerebellar networks as important mediators of tremor, and therefore a likely common site of dysfunction to explain the phenomenologic overlap between impaired postural and gait control with tremor. Further understanding of these mechanisms and networks is of crucial importance in the development of new treatments, particularly surgical or minimally invasive lesional therapies.

Isolated Nocturnal Occurrence of Orofacial Dyskinesias in N-methyl-D-aspartate Receptor Encephalitis-A New Diagnostic Clue

Background

The syndrome of anti-N-methyl-D-aspartate receptor encephalitis is classically associated with a combination of limbic dysfunction, dysautonomia, central hypoventilation and movement disorders. On clinical grounds, the diagnosis is often supported by the presence of generalized dyskinesias in a patient with encephalopathy and catatonic signs. Orofacial dyskinesias have been recognized as characteristic of the disorder but can be absent in some patients. Pure psychiatric syndromes without movement disorders have also been described.

Methods and Results

The authors describe 2 male patients who presented with prominent neuropsychiatric symptoms without movement disorders during wakefulness but isolated orofacial dyskinesias during sleep. In 1 patient, this observation supported the early introduction of immunotherapy; and, in both patients, the clinical outcome was excellent.

Conclusions

Careful history and nocturnal examination may reveal orofacial dyskinesias in patients with N-methyl-D-aspartate receptor encephalitis who have apparent pure psychiatric manifestations.

[Deep brain stimulation in Parkinson's disease. Preliminary outcomes]

BACKGROUND

Parkinson's disease justifies the use of deep brain stimulation (DBS) in certain patients who suffer from this condition. We present mid-term and long-term post-surgical outcomes in a cohort of 60 patients, who underwent DBS in the Hospital de Especialidades at Centro Médico Nacional Siglo XXI, in Mexico City.

METHODS

Patients underwent conventional stereotactic surgery with FrameLink software (Medtronics Inc). This technique consisted in the presurgical evaluation, the placement of stereotactic frame, imaging studies, preoperative planning procedure, microrecording, macrostimulation, as well as the placement of electrodes and generators in two phases. The variables were included in a data platform for Excel management. It was also included a variety of measurement instruments for data comparison. As a standard measure, it was used the Unified Parkinson Disease Rating Scale (UPDRS) before the surgery and at 3, 12, and 36 months.

RESULTS

60 patients underwent surgery: 41 men and 19 women, with an average age of 56.5 years (39-70). There were good results in the majority of patients with preoperative UPDRS and at 3, 12 and 36 months of 79.57, 66.85, 65.29 and 58.75, respectively (p < 0.0001). There were complications in nine patients (15 %) and they were managed in a conservative manner.

CONCLUSIONS

Postsurgical outcomes were from good to excellent in the majority of patients. Complications were minimal and conservatively managed. We propose the use of this procedure in a selected group of Parkinson's patients.

Low specificity and sensitivity of smell identification testing for the diagnosis of Parkinson's disease

OBJECTIVE

The aim of this study is to determine if the University of Pennsylvania's Smell Identification Test (UPSIT) is an accurate diagnostic tool for olfactory dysfunction in Parkinson's disease (PD).

METHOD

We included 138 non-demented PD subjects and 175 control subjects matched by gender. Smell identification was tested using UPSIT.

RESULTS

The mean number of UPSIT items correctly identified by controls was 27.52 ± 5.88; the mean score for PD subjects was 19.66 ± 6.08 (p=<0.001). UPSIT sensitivity was 79.7% with a specificity of 68.5% using a cut-off score of ≤ 25. The overall accuracy for the diagnosis of PD was of 75.3%.

CONCLUSION

UPSIT accuracy and specificity were lower than what has been previously reported. Our data demonstrates that 17.5% of items of the UPSIT were not well identified by healthy controls. Further research of the identification of a truly cross-cultural test is warranted.

Clinical, imaging, and molecular findings in a sample of Mexican families with pantothenate kinase-associated neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal recessive disorder characterized by iron accumulation in the brain, because of mutations in the PANK2 gene. Phenotypic and genotypic characteristics of 11 patients from five Mexican families with PKAN disease are reported. Sequencing of PANK2 confirmed the diagnosis. The 11 patients had dysarthria associated with dystonia and Parkinsonism in six. Brain magnetic resonance imaging (MRI) showed the 'eye-of-the-tiger' sign in all patients. Three different mutations were identified, a novel one (p.A469P) and two (p.G219V and p.N404I) very rare. Homozygous sibs for the p.G219V mutation had a severe disease progression with early death. Dystonia predominated in the p.A469P/p.N404I compound heterozygous patients. Homozygous for p.N404I showed Parkinsonism, tics and personality and speech disorders. Early and late disease onset and variable expression was present in carriers of the different identified mutations. The 'eye-of-the-tiger' is an excellent neuroimaging hallmark to predict PANK2 mutations. We detected a 'cluster' of patients harboring the p.N404I mutation, strongly suggesting a founder effect for this mutation. This is the first familial clinical-genetic PKAN disease study accomplished in Mexico.

Comparing the accuracy of different smell identification tests in Parkinson's disease: relevance of cultural aspects

OBJECTIVE

The aim of this study is to determine the usefulness of the University of Pennsylvania smell identification test (UPSIT), sniffin sticks (SS-16) and brief smell identification test (B-SIT) to assess smell identification in the Mexican population and its accuracy in discriminating subjects with Parkinson's disease (PD).

METHODS

We included 199 nondemented PD subjects and 199 control subjects matched by gender. Smell identification was tested using the UPSIT and SS-16. Our group obtained B-SIT data from a previous report.

RESULTS

The mean number of UPSIT items correctly identified by controls was 27.3±6; the PD group had a mean score of 19.4±6. UPSIT had a sensitivity of 82% with a specificity of 66% for a cut-off score of ≤25 for detection of PD. The mean number of SS-16 items correctly identified by controls was 10.3±2.2, while the PD group had 7.4±2.8 correct answers. For SS-16, sensitivity was 77.8% and specificity of 71.2% when using a cut-off value of ≤9. Lemon, turpentine and rose had an identification rate below the 25th percentile for all three tests. Odors with an identification rate above the 75th percentile include banana for all three tests, and gasoline, onion and chocolate for UPSIT and B-SIT.

CONCLUSION

The sensitivity and specificity of the smell tests that were evaluated were lower in comparison to other published reports. Cultural biases and smell familiarity may influence the test results. The development of a true cross-culturally adapted smell identification test is warranted may improve test accuracy.

[Profile characterization of Parkinson's disease in Mexico: ReMePARK study]

INTRODUCTION

The Mexican Registry of Parkinson´s disease (ReMePARK) is nested within a multicentric cohort aimed to describe motor, non-motor, and genetic determinants of Parkinson's disease in Mexican patients.

MATERIAL AND METHODS

To date, clinical and demographic data from 1,083 subjects has been obtained. Here we present the demographic and clinical data of the current sample along with its comparison with international reports.

RESULTS

A total of 607 male and 476 female subjects with Parkinson's disease were included. The mean age of the patients was 64.7 ± 12.9 years. The time from onset of symptoms to diagnosis was 2.4 ± 2.6 years. About 34% of subjects had only elementary education. Of the subjects, 54.4% were under treatment with dopamine agonists.

CONCLUSION

Subjects with Parkinson's disease incorporated into ReMePARK are comparable with other international registries, with the exception of the years of formal education, time to diagnosis, and the use of dopamine agonists. The characterization of the Mexican population with Parkinson's disease will improve diagnosis and therapeutic management as well as define research efforts in this area. Finally, registry future directions are presented.

Overweight is more prevalent in patients with Parkinson's disease

Underweight and malnutrition are well documented in Parkinson's disease (PD), while overweight has been less reported. We carried out a cross-sectional study including 177 healthy controls and 177 PD patients attending a tertiary care center. We recorded weight and height for all participants. A statistically significant difference was found in body mass index (BMI) between controls and PD patients (29.1±5.4 versus 27.2±4.7, p<0.001). In the PD Group, two patients were underweight, 32.7% were within normal range, 46.9% had overweight, and 19.2% were obese. Overweight and normal weight were more prevalent in the PD Group (p=<0.01 and <0.001, respectively) when compared to controls. In conclusion, overweight/obesity are common among patients with PD, while underweight is almost negligible.

Clinical determinants of health-related quality of life in Mexican patients with Parkinson's disease

BACKGROUND AND AIMS

Parkinson's disease (PD) is the second most common chronic neurodegenerative disorder. PD is clinically characterized by a constellation of motor and nonmotor symptoms that may have a direct effect on daily activities as well as in the quality of life of the patient. Identifying the symptoms more closely associated with a poor quality of life is central on improving the medical care of the patient. We undertook this study to identify and describe the clinical and demographic factors that predict health-related quality of life among Mexican patients with PD.

METHODS

One hundred seventy-seven patients with Parkinson's disease were included. Patients were evaluated using the following clinimetric instruments: motor subscale of the Unified Parkinson's disease rating scale, Hoehn and Yahr stage, Non-motor Symptoms Questionnaire, Parkinson's disease Questionnaire (PDQ-39) and the Mini Mental Status Examination.

RESULTS

Multivariate analysis showed that the main factors associated with a poor quality of life were motor impairment (β = 0.27, p <0.001) and the number of nonmotor symptoms (β = 2.17, p <0.001). The main nonmotor domains impacting on the quality of life were depression/anxiety (β = 6.36, p <0.001), cardiovascular (β = 5.39, p = 0.001), memory (β = 4.64, p <0.001) and miscellaneous (β = 3.15, p = 0.001).

CONCLUSIONS

Both motor and mainly nonmotor symptoms are negatively associated with health-related quality of life in patients with PD and should be appropriately attended in order to improve patient care.

[Premotor diagnosis of Parkinson's disease]

INTRODUCTION

Parkinson's disease is a neurodegenerative disorder characterized by bradykinesia, resting tremor and rigidity. Pathologically, Parkinson's disease is defined by the presence of Lewy bodies, which result from the aggregation of alpha-synuclein. Braak, et al. have proposed that the aggregation of alpha-synuclein pathology in Parkinson's disease begins in the medulla oblongata and progresses predictably, reaching the substantia nigra in the midbrain after affecting the brain stem. Apart from the motor symptoms of the disease, non-motor symptoms may precede the evoked potentials, and these include cognitive dysfunction, psychiatric disorder, sleep disorders and autonomic dysfunction.

OBJECTIVE

To describe and discuss the non-motor symptoms and diagnostic tests and procedures which may provide a pre-motor diagnosis of Parkinson's disease.

CONCLUSIONS

Non-motor symptoms are now accepted as an integral part of the clinical spectrum of Parkinson's disease and there is evidence to suggest that olfactory dysfunction and sleep disturbances may occur before motor signs. The presence of various non-motor symptoms in conjunction with imaging studies has the potential to detect patients with Parkinson's disease in the pre-motor phase. Nevertheless, a larger number of studies are required, in particular cohort design of subjects in risk.