Abnormal Startle Research Articles

Startle Disease: An Overlooked Symptom of CTNNB1-Related Neurodevelopmental Disorder With Spastic Diplegia and Visual Defects.

Neurodevelopmental disorder with spastic diplegia and visual defect (NEDSDV) is a recently described rare syndrome caused by loss-of-function variations in CTNNB1 gene which includes developmental delay, intellectual deficiency, visual defects, and other features. Startle disease is not present in the classic clinical description and has been reported in only 2 patients so far. We report 12 cases of patients with NEDSDV who present an exaggerated startle response including 1 patient observed in our department and 11 patients recruited by addressing a questionnaire to the members of the Facebook group of families of patients with a CTNNB1 pathogenic variant. We performed an EMG analysis of this abnormal startle response in 1 patient and a genotype-phenotype analysis of startle response in NEDSDV. All 12 patients presented exaggerated startle responses to an unexpected stimulus. They provoked falls in 8 patients, causing injuries in 3, and 3 patients were afraid to walk. This startle disorder corresponds to atypic hyperekplexia. No genotype to phenotype correlation has been found to differentiate NEDSDV with or without startle disease. Our data allow us to refine the phenotypic spectrum of patients affected by CTNNB1-related NEDSDV, suggesting that exaggerated startle reactions may be part of clinical features. A precise questioning on startle disorders should be performed systematically in these patients because they can lead to potentially traumatic falls, while effective treatments are available and can improve quality of life. CTNNB1 study should be considered in patients with startle disease associated with intellectual deficiency.

Syntaxin 4 is essential for hearing in human and zebrafish.

Congenital hearing impairment (HI) is a genetically highly heterogeneous disorder in which prompt recognition and intervention are crucial to optimize outcomes. In this study, we used exome sequencing to investigate a large consanguineous Pakistani family with eight affected individuals showing bilateral severe-to-profound HI. This identified a homozygous splice region variant in STX4 (c.232 + 6T>C), which causes exon skipping and a frameshift, that segregated with HI (two-point logarithm of odds (LOD) score = 5.9). STX4, a member of the syntaxin family, is a component of the SNARE machinery involved in several vesicle transport and recycling pathways. In silico analysis showed that murine orthologue Stx4a is highly and widespread expressed in the developing and adult inner ear. Immunofluorescent imaging revealed localization of STX4A in the cell body, cell membrane and stereocilia of inner and outer hair cells. Furthermore, a morpholino-based knockdown of stx4 in zebrafish showed an abnormal startle response, morphological and developmental defects, and a disrupted mechanotransduction function in neuromast hair cells measured via FM1-43 uptake. Our findings indicate that STX4 dysfunction leads to HI in humans and zebrafish and supports the evolutionary conserved role of STX4 in inner ear development and hair cell functioning.

Glycine Receptor Autoantibodies Impair Receptor Function and Induce Motor Dysfunction.

Impairment of glycinergic neurotransmission leads to complex movement and behavioral disorders. Patients harboring glycine receptor autoantibodies suffer from stiff-person syndrome or its severe variant progressive encephalomyelitis with rigidity and myoclonus. Enhanced receptor internalization was proposed as the common molecular mechanism upon autoantibody binding. Although functional impairment of glycine receptors following autoantibody binding has recently been investigated, it is still incompletely understood. A cell-based assay was used for positive sample evaluation. Glycine receptor function was assessed by electrophysiological recordings and radioligand binding assays. The in vivo passive transfer of patient autoantibodies was done using the zebrafish animal model. Glycine receptor function as assessed by glycine dose-response curves showed significantly decreased glycine potency in the presence of patient sera. Upon binding of autoantibodies from 2 patients, a decreased fraction of desensitized receptors was observed, whereas closing of the ion channel remained fast. The glycine receptor N-terminal residues 29 A to 62 G were mapped as a common epitope of glycine receptor autoantibodies. An in vivo transfer into the zebrafish animal model generated a phenotype with disturbed escape behavior accompanied by a reduced number of glycine receptor clusters in the spinal cord of affected animals. Autoantibodies against the extracellular domain mediate alterations of glycine receptor physiology. Moreover, our in vivo data demonstrate that the autoantibodies are a direct cause of the disease, because the transfer of human glycine receptor autoantibodies to zebrafish larvae generated impaired escape behavior in the animal model compatible with abnormal startle response in stiff-person syndrome or progressive encephalitis with rigidity and myoclonus patients. ANN NEUROL 2020;88:544-561.

Deletion of Mtu1 (Trmu) in zebrafish revealed the essential role of tRNA modification in mitochondrial biogenesis and hearing function.

Mtu1(Trmu) is a highly conserved tRNA modifying enzyme responsible for the biosynthesis of τm5s2U at the wobble position of tRNAGln, tRNAGlu and tRNALys. Our previous investigations showed that MTU1 mutation modulated the phenotypic manifestation of deafness-associated mitochondrial 12S rRNA mutation. However, the pathophysiology of MTU1 deficiency remains poorly understood. Using the mtu1 knock-out zebrafish generated by CRISPR/Cas9 system, we demonstrated the abolished 2-thiouridine modification of U34 of mitochondrial tRNALys, tRNAGlu and tRNAGln in the mtu1 knock-out zebrafish. The elimination of this post-transcriptional modification mediated mitochondrial tRNA metabolisms, causing the global decreases in the levels of mitochondrial tRNAs. The aberrant mitochondrial tRNA metabolisms led to the impairment of mitochondrial translation, respiratory deficiencies and reductions of mitochondrial ATP production. These mitochondria dysfunctions caused the defects in hearing organs. Strikingly, mtu1−/– mutant zebrafish displayed the abnormal startle response and swimming behaviors, significant decreases in the sizes of saccular otolith and numbers of hair cells in the auditory and vestibular organs. Furthermore, mtu1−/– mutant zebrafish exhibited the significant reductions in the hair bundle densities in utricle, saccule and lagena. Therefore, our findings may provide new insights into the pathophysiology of deafness, which was manifested by the deficient modifications at wobble position of mitochondrial tRNAs.

Jumping Frenchmen, Miryachit, and Latah: Culture-Specific Hyperstartle-Plus Syndromes.

In the late 19th century, jumping (French Canadians in Maine, USA), miryachit (Siberia), and latah (Southeast Asia) were among a group of similar disorders described around the world, each of which manifests as an exaggerated startle response with additional late-response features that were felt by some to overlap with hysteria or tics. The later features following the exaggerated startle reaction variably include mimesis (e.g., echopraxia, echolalia) and automatic obedience. These reaction patterns tended to persist indefinitely in affected individuals. Because of their dramatic stimulus-driven behaviors, affected individuals were prone to be teased and tormented by being repeatedly and intentionally startled. Despite clinical overlap between jumping and Tourette syndrome, these entities are now recognized as distinct: in jumping, the key feature is an abnormal startle response, the abnormal reaction is always provoked, and tics are absent, whereas in Tourette syndrome, the key feature is spontaneous motor and vocal tics, although patients with Tourette syndrome may occasionally also have an exaggerated startle response. These disorders have been conceptualized from anthropological, psychodynamic, and neurobiologic perspectives, with no complete resolution to date. Attempts at treatment have been generally unsuccessful, including attempts with bromization and hypnosis, although anecdotal reports of successful deconditioning have been published. In population groups affected, these disorders are usually considered as behavioral peculiarities and not as diseases per se, and there is no apparent tendency to develop disabling mental illness or neurodegenerative disorders. The genesis of these disorders, their cultural and social components, and their interactions with the presumed underlying physiological substrate need further study. Careful descriptive and analytic epidemiological studies are also lacking for all of these disorders.

A rare case of familial hyperekplexia

Familial hyperekplexiaia a rare autosomal dominant or sporadic disorder characterized by abnormal startle reaction elicited by auditory or somatosensory stimuli. Here we report a 3 months old female child presented with complaints of exaggerated startle response followed by shrill cry to tactile stimuli over the face noticed by mother since birth. There was also a positive family history in her father and father’s brother. Neurological examination was normal except for hyperreflexia. Child was evaluated further and investigations like EEG and imaging were done. IEM workup was also done. Investigations were all normal. Hence from the classic diagnostic sign and positive family history, diagnosed as a case of familial hyperekplexia and the child improved after being started on clonazepam.

PP08.9 – 2594: Glycine receptor antibody mediated progressive encephalomyelitis with rigidity and myoclonus (PERM) presenting as an abnormal startle response in an adolescent girl

Objective To describe a young girl in whom stimulus sensitive spasms were a diagnostic clue to the underlying glycine receptor antibody mediated progressive encephalomyelitis with rigidity and myoclonus (PERM) which has been described mainly in adults. Methods We illustrate the clinical data from the case-notes with a video recording of stimulus-sensitive spasms. Results A previously well 15-year-old girl presented with a traumatic head injury after falling down the stairs. The noise from a doorbell had triggered a severe muscle spasm causing the fall. She sustained a complex skull fracture with coup-contrecoup brain injury. She had previously been evaluated over five months for stimulus-sensitive whole body spasms with axial hyperextension without impairment of consciousness. She also had daily stimulus-sensitive myoclonic jerks, headaches and subtle cognitive impairment over the preceding year. Whilst on the paediatric intensive care unit, she was noted to have spontaneous and stimulus-sensitive muscle spasms (EMG duration 360–680 ms with no EEG correlate). She also developed generalised tonic clonic seizures, which were treated with Levetiracetam. A diagnosis of PERM was considered and glycine receptor antibodies were found to be strongly positive in serum and CSF. VGKC-complex antibodies were also weakly positive but GAD and NMDAR antibodies were negative. Oligoclonal bands were positive in CSF but negative in serum. Paraneoplastic antibodies were negative. Brain MRI showed contusions in the right hemisphere. Body imaging did not identify any tumours. Glycine receptor gene analysis is awaited. Her spasms have improved with a residual mild startle response to touch or loud auditory stimuli. She has a residual left hemiparesis. She was not treated with immunomodulation but will be followed up, and immunotherapy considered if she does not continue to improve and antibodies persist. Conclusion Glycine receptor antibody-mediated progressive encephalomyelitis with rigidity and myoclonus can present in children as stimulus-sensitive muscle spasms.

Milestones in clinical neurophysiology

Over the last 25 years, clinical neurophysiology has made many advances in the understanding, diagnosis, and even treatment of different movement disorders. Transcranial magnetic stimulation has been the biggest technical advance. Progress in pathophysiology includes improved knowledge about bradykinesia in Parkinson's disease, loss of inhibition and increased plasticity in dystonia, abnormal startle in hyperekplexia, and various features of psychogenic movement disorders that can aid diagnosis. Studies have been done looking at the use of noninvasive brain stimulation for therapy, but effects are generally small.

Identification of a de novo Lys304Gln mutation in the glycine receptor α‐1 subunit gene in a Korean infant with hyperekplexia

Startle disease or hyperekplexia (STHE; MIM 149400) is a rare disorder that is characterized by marked muscular hypertonia in infancy and an exaggerated startle response to unexpected acoustic or tactile stimuli. Mutations in the gene encoding the alpha-1 subunit of the inhibitory glycine receptor (GLRA1) were reported as causes of STHE. Recently, we encountered a Korean male infant with generalized stiffness that was observed from the first 3 days of life. The abnormal startle response was evident from the fourth week of life, and he showed marked improvement in the startle response and muscle hypertonia after being administered phenobarbital and clonazepam. Direct sequencing analysis of the infant and his parents revealed a de novo variation (c.910A>C) in the GLRA1 gene, resulting in a novel Lys304Gln missense mutation.

Abnormal affective startle modulation in individuals with psychogenical movement disorder

Abnormal affective startle modulation in individuals with psychogenical movement disorder

The movement disorders of Coffin–Lowry syndrome

Coffin–Lowry syndrome (CLS) is an X-linked semi-dominant condition with learning difficulties and dysmorphism caused by mutations in the gene RSK2. Originally, epilepsy was reported as a feature. We and others have since described predominantly sound-startle induced drop attacks that have been labelled ‘cataplexy’, abnormal startle response and hyperekplexia. We sought to clarify why there should be controversy over the type of paroxysmal events. Review of the literature and our patients confirmed that each centre had studied only a small numbers of individuals (mean=2). The type of movement disorder varied both with age and between individuals. One individual might have more than one movement disorder. One of our adult patients had several types of movement disorder and epilepsy that merged seamlessly: there was true cataplexy triggered by telling a joke, something close to cataplexy (‘cataplexy’) triggered by sound-startle, a predominantly hypertonic reaction varying from hyperekplexia to a more prolonged tonic reaction resembling startle epilepsy, and true unprovoked epileptic seizures. In the large database of the Coffin–Lowry Syndrome Foundation family support group, 34 of 170 (20%) individuals with CLS and known age had ‘drop attacks’ and an additional 9 (5%) of these had additional epileptic seizures. The onset of such events was usually after age 5 years, prevalence peaking at 15–20 years (27%). Many became wheelchair bound as a result. This unique combination of more than one non-epileptic movement disorder and epilepsy deserves further semiological and genetic study both for the patients with CLS and for the wider implications.

Startle epilepsy complicating aspartylglucosaminuria

A 21-year-old right-handed man with definite diagnosis of aspartylglucosaminuria (AGU) presented with a 5-year history of progressive severe gait disturbance with frequent falls and generalized epileptic seizures triggered by unexpected stimuli. At one time, he was confined to a wheelchair because of the frequent falls. Electromyogram recording showed a large, excessive and not habituating motor startle response, with the classical and stereotyped order of muscle recruitment. During video-polygraphic recording, we recorded a reflex generalized tonic seizure triggered by a loud, unexpected acoustic stimulus. Brain magnetic resonance (MR) revealed no structural abnormality. A diagnosis of abnormal startle and startle epilepsy (SE) was made. The addition of clonazepam to valproate and phenobarbital led to a dramatic improvement in his abnormal startle and SE, and the patient was able to walk alone unaided. This report illustrates, for the first time, that abnormal startle and SE may occur in AGU and complicate its clinical picture. Recognition of this entity in AGU is important, as progressive gait disorder with frequent falls could be easily misinterpreted as an additional irreversible manifestation of the ongoing neurological deterioration characteristic of AGU.

Small Maf compound mutants display central nervous system neuronal degeneration, aberrant transcription, and Bach protein mislocalization coincident with myoclonus and abnormal startle response.

The small Maf proteins form heterodimers with CNC and Bach family proteins to elicit transcriptional responses from Maf recognition elements (MAREs). We previously reported germ line-targeted deficiencies in mafG plus mafK compound mutant mice. The most prominent mutant phenotype was a progressive maf dosage-dependent neuromuscular dysfunction. However, there has been no previous report regarding the effects of altered small-maf gene expression on neurological dysfunction. We show here that MafG and MafK are expressed in discrete central nervous system (CNS) neurons and that mafG::mafK compound mutants display neuronal degeneration coincident with surprisingly selective MARE-dependent transcriptional abnormalities. The CNS morphological changes are concurrent with the onset of a neurological disorder in the mutants, and the behavioral changes are accompanied by reduced glycine receptor subunit accumulation. Bach/small Maf heterodimers, which normally generate transcriptional repressors, were significantly underrepresented in nuclear extracts prepared from maf mutant brains, and Bach proteins fail to accumulate normally in nuclei. Thus compound mafG::mafK mutants develop age- and maf gene dosage-dependent cell-autonomous neuronal deficiencies that lead to profound neurological defects.

153 An abnormal proprioceptive startle in infants implies grave neurological outcome

153 An abnormal proprioceptive startle in infants implies grave neurological outcome

Hyperekplexia: abnormal startle response due to glycine receptor mutations.

Hyperekplexia is a rare but well-delineated clinical syndrome of pathological startle response and neonatal hypertonia. Many cases result from mutations in the alpha 1 subunit of the glycine receptor (GLRA 1). The clinical features, management and recent genetic studies of hyperekplexia are reviewed. Diagnosis of the disorder should not be difficult, if one is aware of the syndrome. The treatment of first choice is with the benzodiazepine drug clonazepam, which often causes a dramatic although incomplete diminution of startle. Both recessive and dominant mutations in GLRA 1 have been found in affected individuals. The study of mouse mutants with startle phenotypes suggests that the remainder of cases may well be due to mutations in the beta subunit of the glycine receptor. Hyperekplexia is the first human disease shown to result from mutations within a neurotransmitter gene. The demonstration of both dominant and recessive inheritance resulting from different mutations in the same gene is of considerable interest, as other neuropsychiatric disorders may result from mutations in ligand-gated ion channels. Mutation analysis of GLRA 1 is also likely to be useful as an aid to genetic counselling and in diagnostic evaluation of neonatal hypertonia.

Auditory startle response during exposure to war stress

This report describes the immediate effect of war stress on physiological measures of the auditory startle responses (ASRs). Ten healthy Israeli subjects were examined 4 months before the Gulf war, during a missile alert on the first day of the war, and 8 months after the war. The magnitude and rate of habituation of orbicularis oculi electromyogram (EMG), heart rate (HR), and skin conductance (SC) responses to 15 consecutive presentations of 95-dB, 0-rise time, 1,000-Hz pure tones were recorded on each occasion, along with self-reports of anxiety. The group's anxiety scores were significantly higher during the war. ASRs, in contrast, remained stable across exposure conditions. However, a decrease in SC habituation was observed in few individuals during the war, and may illustrate a distinctive vulnerability to stress. The results are discussed in light of recent findings of abnormal startle response in posttraumatic stress disorder (PTSD).

Hyperekplexia, a cause of neonatal apnea: a case report

We report a case of non-familial hyperekplexia which characteristically developed apnea and feeding difficulties in the neonatal period. The abnormal startle response was evident from the second week of life onwards. The infant showed a marked improvement of the startle response and muscle hypertonia with clonazepam. Clobazam was also tried with no apparent response. A prominent long latency C response was observed on EMG examination, suggesting a possible cortical neuronal hyperexcitability origin for the abnormal startle response observed in hyperekplexia.

Genetic Mapping and Evaluation of Candidate Genes for Spasmodic, a Neurological Mouse Mutation with Abnormal Startle Response

Spasmodic (spd) is a recessive mouse mutation characterized by a prolonged righting reflex, fine motor tremor, leg clasping, and stiffness. Using an intersubspecific backcross that segregates spd, we placed spd on Chr 11 with the following gene order: Adra-1-3.8 ± 2.1 cM-Pad-1-6.3 ± 2.7-(spd, Anx-6, Csfgm, Glr-1, Il-3, Il-4, Il-5, Sparc)-9.1 ± 2.4-D11 Mit5-2.2 ± 1.5-Asgr-1. This localization eliminated the α1-adrenergic receptor (Adra-1) and the α1 and γ2 subunits of the GABAA receptor as candidate genes. Two other promising candidate genes, annexin VI (Anx-6) and a glutamate receptor (Glr-1), were mapped to within 2.1 cM of the spd locus. Although no recombination was observed between spd and Anx-6 or Glr-1, no evidence was obtained for a lesion in either gene. The presence of normal Anx-6 and Glr-1 mRNA transcripts was confirmed by Northern blot analysis, in situ hybridization, and DNA sequence analysis. The localization of Anx-6 and Glr-1 extends the known synteny homology between human chromosome 5q21-q31 and mouse Chr 11 and reveals the probable chromosomal location of the human counterpart to spd. Synteny homology and phenotypic similarities suggest that spasmodic mice may be a genetic model for the inherited human startle disease, hyperekplexia (STHE).

Neonatal hyperekplexia: a case report.

We report the case of a baby with transient generalized stiffness noticeable from the first days of life, hyperreflexia, massive jerks in response to sudden tactile and acoustic stimuli, and long-lasting myoclonic jerks closely resembling epileptic seizures. The father and paternal grandfather both had hyperekplexia. At age 3 years, the child had normal psychomotor development and persistent abnormal startle response to unexpected sounds or touch.

Human startle reflex: technique and criteria for abnormal response

Because quantitative norms for the normal audiogenic startle response to repeated stimuli have not been previously reported, we now describe a technique for eliciting the startle response and anlaysing its habituation with repeated stimuli. We used binaural 105 dB tones delivered in 5 blocks of 4 tones. Successive blocks were separated by a 5 min period without tones stimuli and had progressively shorter inter-stimulus intervals (ISIs) beginning with 5 min in the first block and reducing to 1 min in the final, fifth block. We contrast the response and its habituation in a group of 8 normal subjects with that in a patient with clinically exaggerated startle. Based on the differences observed, we propose that the following criteria may be used to ascertain an abnormally increased startle response: (1) excessive duration of the myogenic response; (2) persistence of extracranial responses after the initial two blocks of stimuli; and (3) reduced habituation of the response (as measured by decreases in response duration and in the area under the curve of rectified EMG for the orbicularis oculi myogenic response). Our patient was abnormal on each of these measures. This result is consistent with past qualitative reports which have indicated that abnormal startle is associated both with excessive startle and with subnormal habituation. Study of further patients with hyperekplexia will be necessary to either confirm our data or modify our proposed criteria.