Primitive reflexes in Parkinson's disease

Primitive reflexes and dementia in older adults: a meta-analysis of observational and cohort studies

Primitive reflexes (PRs) are clinical signs that indicate diffuse cerebral dysfunction and frontal lesions. We aimed to present a comprehensive analysis of the prevalence and risk of PRs in patients with dementia. English-language articles published from January 1990 to April 2021 were searched in PubMed, ScienceDirect, Cochrane, and Web of Science with keywords. The titles and abstracts of the identified articles were screened to identify potentially relevant papers. Odds ratios and risk ratios were extracted with 95% confidence intervals and combined using the random-effects model after logarithmic transformation. The prevalence in dementia patients was also combined using the random-effects model. This meta-analysis involved 29 studies. The snout reflex (48% of cases) was the most prevalent. It was found that the risk of PRs in individuals with dementia was significantly elevated, ranging from 13.94 to 16.38 times higher than in healthy controls. The grasp reflex exhibited the highest risk for dementia. This meta-analysis showed that the prevalence and the risk of PRs is high in older patients with dementia. Therefore, PRs, especially the grasp reflex, should be carefully assessed as a part of routine physical examination in the diagnostic process for dementia.

Video-based analysis of the blink reflex in Parkinson's disease patients

We developed a video-based tool to quantitatively assess the Glabellar Tap Reflex (GTR) in patients with idiopathic Parkinson's disease (iPD) as well as healthy age-matched participants. We also video-graphically assessed the effect of dopaminergic medication on the GTR in iPD patients, as well as the frequency and blinking duration of reflex and non-reflex blinks. The Glabellar Tap Reflex is a clinical sign seen in patients e.g. suffering from iPD. Reliable tools to quantify this sign are lacking.

METHODS

We recorded the GTR in 11 iPD patients and 12 healthy controls (HC) with a consumer-grade camera at a framerate of at least 180 images/s. In these videos, reflex and non-reflex blinks were analyzed for blink count and blinking duration in an automated fashion.

RESULTS

With our setup, the GTR can be extracted from high-framerate cameras using landmarks of the MediaPipe face algorithm. iPD patients did not habituate to the GTR; dopaminergic medication did not alter that response. iPD patients' non-reflex blinks were higher in frequency and higher in blinking duration (width at half prominence); dopaminergic medication decreased the median frequency (Before medication-HC: p < 0.001, After medication-HC: p = 0.0026) and decreased the median blinking duration (Before medication-HC: p = 0.8594, After medication-HC: p = 0.6943)-both in the direction of HC.

CONCLUSION

We developed a quantitative, video-based tool to assess the GTR and other blinking-specific parameters in HC and iPD patients. Further studies could compare the video data to electromyogram (EMG) data for accuracy and comparability, as well as evaluate the specificity of the GTR in patients with other neurodegenerative disorders, in whom the GTR can also be present.

SIGNIFICANCE

The video-based detection of the blinking parameters allows for unobtrusive measurement in patients, a safer and more comfortable option.

Diagnostic accuracy of glabellar tap sign for Parkinson's disease

Glabellar tap or reflex (GR) is an old bedside clinical test used in the diagnostics of Parkinson’s disease (PD), but its diagnostic value is unclear. This study examines the diagnostic validity and reliability of GR in PD in relation to brain dopaminergic activity. GR was performed on 161 patients with PD, 47 patients with essential tremor (ET) and 40 healthy controls immediately prior to dopamine transporter (DAT) [¹²³I]FP-CIT SPECT scanning. The binding ratios were investigated with consideration of the GR result (normal/abnormal). In addition, the consistency of the GR was investigated with 89 patients after a mean follow-up of 2.2 years. PD and ET patients had higher GR scores than healthy controls (p < 0.001), but there was no difference in GR between PD and ET patients (p = 0.09). There were no differences in the ratio of abnormal to normal GRs between the PD and ET groups (73% vs. 64% abnormal, respectively, p = 0.13) or in DAT binding between PD patients with abnormal and normal GRs (p > 0.36). Over follow-up, the GR changed from abnormal to normal in 20% of PD patients despite the presence of clinically typical disease. The sensitivity and specificity of GR for differentiating PD from ET were 78.3% and 36.2%, respectively. Although GR has been used by clinicians in the diagnostics of PD, it does not separate PD from ET. It also shows considerable inconsistency over time, and abnormal GR has no relationship with dopamine loss. Its usefulness should be tested for other clinical diagnostic purposes.

Nociceptive Primitive Reflexes in Neurologically and Cognitively Healthy Aging Subjects

BACKGROUND

To assess the prevalence of three nociceptive primitive reflexes (nPR), i.e., glabellar tap, snout reflex, and palmomental reflex, in neurologically and cognitively healthy (NCH) aging subjects.

OBJECTIVE

To investigate whether nPR are cross-sectionally associated with white matter hyperintensities (WMH), lacunes, atrophy of the caudate nuclei, and global brain atrophy.

METHODS

A total of 1246 NCH subjects aged 45-91 years were included in the study and underwent standard brain MRI. Atrophy of the caudate nuclei and global brain atrophy were assessed through the bicaudate ratio (BCr) and lateral ventricles to brain ratio (LVBr), respectively. WMH were assessed through visual rating scales. Lacunes were also rated. Association of nPR with vascular risk factors/diseases and imaging findings was evaluated using logistic regression analysis.

RESULTS

nPR were exhibited by 33.1% of subjects and increased with age. Subjects with nPR performed less than subjects without nPR in tests evaluating global cognition, executive functions, attention, and language. Snout reflex was the most common nPR, followed by glabellar tap and palmomental reflex. Glabellar tap was associated with parieto-temporal WMH, BCr, and LVBr; snout reflex was associated with frontal lacunes, temporal WMH, BCr, and LVBr; palmomental reflex was associated with parieto-occipital WMH, basal ganglia lacunes, BCr, and LVBr.

CONCLUSIONS

This study demonstrates that in NCH aging individuals, nPR are associated with WMH, lacunes, BCr, and LVBr and are probably a warning sign of incipient cognitive decline. Therefore, NCH subjects presenting nPR should manage their vascular risk factors/vascular diseases rigorously in order to prevent or delay progression of small vessel disease, and future neurological and cognitive disabilities.

Humanoid Cognitive Robots That Learn by Imitating: Implications for Consciousness Studies

While the concept of a conscious machine is intriguing, producing such a machine remains controversial and challenging. Here, we describe how our work on creating a humanoid cognitive robot that learns to perform tasks via imitation learning relates to this issue. Our discussion is divided into three parts. First, we summarize our previous framework for advancing the understanding of the nature of phenomenal consciousness. This framework is based on identifying computational correlates of consciousness. Second, we describe a cognitive robotic system that we recently developed that learns to perform tasks by imitating human-provided demonstrations. This humanoid robot uses cause–effect reasoning to infer a demonstrator’s intentions in performing a task, rather than just imitating the observed actions verbatim. In particular, its cognitive components center on top-down control of a working memory that retains the explanatory interpretations that the robot constructs during learning. Finally, we describe our ongoing work that is focused on converting our robot’s imitation learning cognitive system into purely neurocomputational form, including both its low-level cognitive neuromotor components, its use of working memory, and its causal reasoning mechanisms. Based on our initial results, we argue that the top-down cognitive control of working memory, and in particular its gating mechanisms, is an important potential computational correlate of consciousness in humanoid robots. We conclude that developing high-level neurocognitive control systems for cognitive robots and using them to search for computational correlates of consciousness provides an important approach to advancing our understanding of consciousness, and that it provides a credible and achievable route to ultimately developing a phenomenally conscious machine.

Primitive reflexes distinguish vascular parkinsonism from Parkinson's disease

OBJECTIVES

Although vascular parkinsonism (VP) occurs frequently in the elderly, its clinical features have not been investigated in detail, particularly in comparison with Parkinson's disease (PD). The goal of this study is to clarify the diagnostic value of pathological reflexes in differentiating between VP and PD.

PATIENTS AND METHODS

In 132 patients with PD and 55 with VP, pathological reflexes, including snout reflex (SR), palmomental reflex (PMR), corneomandibular reflex (CMR), jaw reflex (JR), Hoffmann reflex (HR), and extensor plantar response (EPR), were evaluated.

RESULTS

The percentage of each pathological reflex elicited in two groups (VP:PD) was as follows: SR (78:30), PMR (53:26), CMR (9:6), JR (33:12), HR (29:11), and EPR (25:8). The prevalence of pathological reflexes, except for CMR, was significantly higher in the VP patients than in the PD patients. In particular, SR and PMR were more frequent than upper motor neuron signs in the VP patients. The sensitivity and specificity of either SR or PMR for VP were 84% and 82%.

CONCLUSION

Snout and palmomental reflexes are useful tools in the differentiation between VP and PD.

Developmental reflexes and 31P Magnetic Resonance Spectroscopy of basal ganglia in antipsychotic-naive schizophrenia

The study examined the high energy-phosphate metabolism of basal ganglia in antipsychotic-naive schizophrenia patients with and without developmental reflexes in comparison to healthy subjects. Nineteen antipsychotic-naive schizophrenics of whom 11 had developmental reflexes and 26 age-sex-matched healthy subjects without developmental reflexes underwent in-vivo 2-D 31P Magnetic Resonance Spectroscopy of basal ganglia on a 1.5-T scanner. Mean age-at-onset of psychosis was significantly lower in patients with developmental reflexes. Mean PCr/Total ATP ratio in bilateral basal ganglia was lower in patients than healthy subjects. The ratio was the least in patients with developmental reflexes (F=10.7; df=2, 42; p<0.001). Schizophrenia patients with developmental reflexes had the lowest PCr/Total ATP ratio in basal ganglia indicating more severe metabolic abnormality. These patients had younger age-at-onset of psychosis. Together, this suggests neurodevelopmental etiopathogenesis in schizophrenia.

Cortical release signs in psychiatry

OBJECTIVE

To review the role of cortical release signs (CRS) in neuropsychiatry.

METHOD

A thorough literature review was conducted using Medline and Psychlit databases, and other relevant references available to the authors.

RESULTS

A number of neurological abnormalities are reported at elevated rates in neuropsychiatric conditions. CRS are a group of primitive reflexes that are present in the neonate but become inhibited as the infant central nervous system (CNS) develops, only to later re-emerge in the context of CNS disease. The clinical elicitation and interpretation of each CRS is described with reference to its neurobiology. The prevalence of CRS in schizophrenia, affective disorder, obsessive-compulsive disorder, Alzheimer's disease, vascular dementia, frontotemporal dementia and other neuropsychiatric illness allows for their use in the clinical management of these patients, including diagnostic assessment, treatment monitoring and prognosis.

CONCLUSIONS

A number of issues complicate their interpretation in neuropsychiatric illness, including the apparent high base rate of some CRS in non-clinical populations, their increasing prevalence with age, lack of specificity and uncertainty over what constitutes an 'abnormal' response. In some circumstances, CRS may assist in diagnostic differentiation and illness staging.

Parkinson's disease and anaesthesia

Parkinson's disease is an increasingly common disease of elderly patients who present a particular anaesthetic challenge. This review explores the epidemiology, aetiology, pathogenesis, and pathophysiology of the condition, particularly the possible role of genetic factors. The clinical features are described in detail and recent advances in medical management are highlighted. Controversies surrounding the use of the newer drugs and possible advances in neurosurgical interventions are discussed. Particular anaesthetic problems in patients with Parkinson's disease are respiratory, cardiovascular, and neurological. Potential drug interactions are described and recommendations are made about suitable anaesthetic techniques.

The palmomental reflex: a useful clinical sign?

The palmomental reflex, an involuntary contraction of the mentalis muscle of the chin caused by stimulation of the thenar eminence, can be tested easily and rapidly. Its presence may alert the clinician to the possibility of cerebral pathology. However, the reflex is often present in normal people and may be absent in disease states. Testing merely for the presence or absence of the reflex therefore lacks both specificity and sensitivity. A strong, sustained, and easily repeatable contraction of the mentalis muscle, which can be elicited by stimulation of areas other than the palm, is more likely to indicate cerebral damage.

Electrophysiological assessments of primitive reflexes in stroke patients

OBJECTIVE

To evaluate the primitive reflexes by electrophysiological assessments and their correlation with the cognitive and physical functioning of stroke patients.

METHODS

Electrophysiological studies of primitive reflexes including jaw jerk, snout reflex, glabellar reflex, and corneomandibular reflexes were performed in 38 stroke patients and 26 normal controls. Cognitive function of patients was assessed by Modified Mini-Mental State (3MS) Examination and logical memory test. The Chinese Functional Independence Scale (CFIS) was used to evaluate the physical functioning and social domains of stroke patients.

RESULTS

The presence rate of primitive reflexes was higher in stroke patients than in normal controls. Wave amplitude of snout and corneomandibular reflexes obtained from stroke patients was greater than those from controls. No definite difference in reflex conduction latencies was observed between the two groups. A regression relationship was noted between the wave amplitude of snout reflexes and the 3MS and CFIS scores of stroke patients.

CONCLUSION

Primitive reflexes can be measured by electrophysiological assessments. The results may serve as an objective and useful parameter in evaluation of cognition and physical functioning of stroke patients.

Discriminating mild parkinsonism: methods for epidemiological research

Methods for the efficient and accurate detection of parkinsonism are essential for epidemiological studies. We sought to determine whether parkinsonism could be detected by a neurologist from a videotaped assessment and whether neurobehavioral methods (motor, cognitive, and sensory) discriminated between patients with Parkinson's disease (PD) and controls. Fifteen patients with mild PD (Hoehn and Yahr I-III) were compared to 15 age-, sex-, and education- matched controls. Each participant underwent a videotaped neurological examination (based on the Unified Parkinson's Disease Rating Scale, UPDRS), administered by a trained technician, and reviewed by a neurologist, as well as a series of neurobehavioral tests. The neurologist identified PD patients with 86% sensitivity and 100% specificity. Among the neurobehavioral tests, finger tapping, combined with one or more among olfaction, visual contrast sensitivity, or Paired Associates Learning, correctly classified 90%, or more, of subjects. Individual psychological tests did not discriminate reliably between groups. We conclude that videotaped assessments of parkinsonism or objective tests of motor and sensory function can accurately detect patients with PD. Both approaches have potential for identifying PD cases, but the latter may be more efficient for screening.

Effect of diabetes on some primitive reflexes

Primitive reflexes (PRs) are present in newborns; they disappear as the brain matures and increase in frequency in healthy elderly individuals. Primitive reflexes are more frequent in some neurological disorders than in age-matched controls. The aim of this study was to investigate the effect of diabetes on some PRs. We examined three PRs (glabellar tap, snout and palmomental reflexes) in 376 subjects: 111 normal age-matched controls, 60 patients with cerebrovascular disease (CVD) and 205 patients with type 2 diabetes mellitus. The latter patients were divided into three groups: (1) diabetics without neurological complications (D); (2) diabetics with cerebrovascular disease (D-CVD); and (3) diabetics with polyneuropathy (D-PN). The frequency of PRs was increased in CVD, unchanged in D-CVD (except palmomental) and greatly reduced in D and D-PN. It is possible that the vascular lesions in perforating arteries of the pons in diabetic subjects, previously studied in some pathological reports, can account for the reduced occurrence of primitive reflex responses.

The basal ganglia: focused selection and inhibition of competing motor programs

The basal ganglia comprise several nuclei in the forebrain, diencephalon, and midbrain thought to play a significant role in the control of posture and movement. It is well recognized that people with degenerative diseases of the basal ganglia suffer from rigidly held abnormal body postures, slowing of movement, involuntary movements, or a combination of these a abnormalities. However, it has not been agreed just what the basal ganglia contribute to normal movement. Recent advances in knowledge of the basal ganglia circuitry, activity of basal ganglia neurons during movement, and the effect of basal ganglia lesions have led to a new hypothesis of basal ganglia function. The hypothesis states that the basal ganglia do not generate movements. Instead, when voluntary movement is generated by cerebral cortical and cerebellar mechanisms, the basal ganglia act broadly to inhibit competing motor mechanisms that would otherwise interfere with the desired movement. Simultaneously, inhibition is removed focally from the desired motor mechanisms to allow that movement to proceed. Inability to inhibit competing motor programs results in slow movements, abnormal postures and involuntary muscle activity.

Neurological findings in the normal elderly: prevalence and relationships with memory performance

Data on the presence of neurological signs in the normal elderly are scanty, and data on their possible relationships to memory performances are not available. Three-hundred and ninety-six subjects born in 1925 and living in Pavia, who were recruited for a larger study on memory impairment in the elderly, underwent a standardized neurological examination (SNE) consisting of 22 items, an anamnestic interview and a memory test battery. A high number of signs was found, particularly for regressive reflexes (snout in 50% of cases). There was a tendency for several alterations to be found in the same subject. Accordingly, four clusters of signs were identified. Diabetes mellitus, hypertension, heart disease or past head trauma were not consistently associated with SNE scores. While memory impairment was also not consistently associated with SNE scores, there was a higher tendency for memory-impaired subjects to show at least one abnormal SNE score.

Primitive reflexes in healthy, adult volunteers and neurological patients: methodological issues

A study was made to determine whether two experienced clinicians elicited and scored primitive reflexes (PR) differently and whether reliability could be improved by standardization. Three studies were carried out, using a protocol for the examination of 14 PR. In the first study with 31 healthy young subjects, two investigators found virtually no difference in the routine neurological examination. However, the interobserver agreement was very poor, indicating the need for a further improvement of the PR protocol. In the second study, 30 neurological patients were examined with an improved, more explicit and standardized protocol, in which the amplitude and the persistence of the reflex were scored separately. Interobserver agreement improved considerably, and was high for amplitude as well as persistence. In the third study, 36 neurological patients were examined twice by one investigator within 2 weeks. Good to excellent intraobserver agreement was found. No pathognomonic or strictly localizing reflex could be distinguished.