Abhishek Lenka

Abhishek Lenka
University of Texas Southwestern Medical Center | UT Southwestern · Department of Neurology and Neurotherapeutics

MBBS, PhD (Clinical Neurosciences)

About

127
Publications
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Introduction
Abhishek Lenka works in the Division of Autonomic Disorders at the University of Texas Southwestern Medical Center, Dallas, TX. He completed a Movement Disorders fellowship and Neurology residency from Baylor College of Medicine, Houston, and Georgetown University, Washington, DC, respectively. He pursued a Ph.D. (Neurosciences) from NIMHANS, Bangalore, India. His areas of research/clinical interest are dysautonomia in Lewy body diseases and cognitive and psychiatric issues in patients with PD.

Publications

Publications (127)
Article
Objective: Psychosis is one of the most debilitating complications of Parkinson disease (PD). Although research on PD psychosis has been focused on the study of well-structured visual hallucinations (VH), currently accepted National Institute of Neurological Disorders and Stroke-National Institute of Mental Health diagnostic criteria emphasize min...
Article
Objective The objective of the current study was to compare the microstructural integrity of the white matter (WM) tracts in patients having Parkinson disease (PD) with and without psychosis (PD-P and PD-NP) through diffusion tensor imaging (DTI). Methods This cross-sectional study involved 48 PD-NP and 42 PD-P who were matched for age, sex, and e...
Article
BACKGROUND Parkinson's disease with orthostatic hypotension (PD+OH) can be difficult to distinguish clinically from the parkinsonian form of multiple system atrophy (MSA‐P). Previous studies examined cardiac sympathetic neuroimaging to differentiate PD from MSA but without focusing specifically on PD+OH vs. MSA‐P, which often is the relevant differ...
Article
Purpose: Pure autonomic failure (PAF) is a rare disease characterized by neurogenic orthostatic hypotension (nOH), no known secondary cause, and lack of a neurodegenerative movement or cognitive disorder. Clinically diagnosed PAF can evolve (“phenoconvert”) to a central Lewy body disease [LBD, e.g., Parkinson’s disease (PD) or dementia with Lewy bo...
Article
Introduction: Although there has been substantial progress in research and innovations in symptomatic treatments, similar success has not been achieved in disease-modifying therapy (DMT) for Parkinson’s disease (PD). Considering the enormous motor, psychosocial and financial burden associated with PD, safe and effective DMT is of paramount importan...
Article
Full-text available
Background and Objectives: Psychosis is one of the major neuropsychiatric non-motor symptoms of Parkinson’s disease (PD). Prolonged latency and decreased amplitude of the P300 event-related potential (ERP) is a potential neurophysiologic biomarker of deeper neurocognitive deficits in PD. We aimed to characterize electroencephalogram (EEG)/ERP para...
Article
BACKGROUND AND OBJECTIVES: Corticobasal syndrome (CBS) is a complex of symptoms and signs comprising limb rigidity, bradykinesia, dystonia, myoclonus, apraxia, cortical sensory loss, and a variety of cognitive and language impairments. CBS is commonly seen in tauopathies. Striking asymmetry in clinical and imaging findings in CBS raises questions a...
Conference Paper
OBJECTIVE: To determine the prevalence of apraxia of eyelid opening (AOELO) in patients with movement disorders evaluated at the Parkinson’s Disease Center and Movement Disorders Clinic, Baylor College of Medicine, Houston, TX, and to explore its demographic and clinical correlates. BACKGROUND: AOELO is the inability to voluntarily open the eyes i...
Conference Paper
OBJECTIVE: This study aims to systematically review the array of movement disorders observed in patients diagnosed with brain sagging syndrome (BSS) secondary to spontaneous intracranial hypotension (SIH). BACKGROUND: While BSS typically presents with chronic orthostatic headaches and behavioral/cognitive changes, a subset of patients may manifest...
Article
Full-text available
BACKGROUND: Spontaneous intracranial hypotension (SIH), a treatable condition that stems from spinal leakage of cerebrospinal fluid, usually presents with orthostatic headache, nausea, vomiting, dizziness, and tinnitus. A subset of patients, especially those with sagging of brain structures (“brain sagging syndrome”), develop several movement abnor...
Article
INTRODUCTION Tourette syndrome (TS) is a childhood-onset neurobehavioral disorder characterized by tics. Pharmacotherapy is advised for patients whose symptoms affect their quality of life. AREAS COVERED The authors review the tic phenomenology and TS diagnostic criteria. The bulk of this article focuses on pharmacotherapeutic options for treating...
Article
The term “catatonia” was introduced by German psychiatrist Karl Kahlbaum in 1874. Although historically tied to schizophrenia, catatonia exhibits a diverse range of phenotypes and has been observed in various medical and neuropsychiatric conditions. Its intrinsic movement characteristics and association with hypokinetic and hyperkinetic phenomenolo...
Article
The term “extrapyramidal system/symptoms/signs” and the acronym “EPS” have been abundantly used in neurology and psychiatry literature for more than a century. However, EPS has been increasingly criticized, especially by movement disorder neurologists, for its lack of clinical, anatomical, and physiologic definition. Contrary to traditional assumpt...
Article
Full-text available
OBJECTIVE: Homer1, a postsynaptic protein coded by the HOMER1 gene, presumably has a role in homeostatic plasticity that dampens neuronal responsiveness when the input activity is too high. HOMER1 polymorphism has been studied in major psychiatric disorders such as schizophrenia. The objective of this study is to investigate if polymorphisms of th...
Article
Dyskinesia is a common complication of long-term levodopa therapy in patients with Parkinson’s disease (PD), which often worsens the quality of life. It is usually dose-dependent and emerges possibly due to pulsatile stimulation of dopamine receptors. Delineating the pattern of dyskinesia is crucial for determining the most effective therapeutic ap...
Article
Full-text available
Essential tremor (ET) is a chronic, progressive neurological disease that may negatively affect patients’ lives. While there has been considerable progress in ET research, some fundamental issues remain unaddressed. One such issue is disease staging. Staging schemes have inherent value and are part of the dialogue that clinicians have with other mo...
Article
Full-text available
Psychosis is a debilitating non-motor symptom of Parkinson’s disease that commonly manifests with illusions, presence/passage hallucinations, and well-formed visual hallucinations. Parkinson’s disease psychosis (PDP) is associated with several negative repercussions such as increased caregiver distress and high rates of nursing home placement, heal...
Article
Full-text available
Psychotic symptoms occur in a majority of schizophrenia patients and in ~50% of all Parkinson’s disease (PD) patients. Altered grey matter (GM) structure within several brain areas and networks may contribute to their pathogenesis. Little is known, however, about transdiagnostic similarities when psychotic symptoms occur in different disorders, suc...
Article
Dystonia and tremor are the two most commonly encountered hyperkinetic movement disorders encountered in clinical practice. While there has been substantial progress in the research on these two disorders, there also exists a lot of gray areas. Entities such as dystonic tremor and tremor associated with dystonia occupy a major portion of the “gray...
Article
Full-text available
BACKGROUND: Peripherally-induced movement disorders (PIMD) should be considered when involuntary or abnormal movements emerge shortly after an injury to a body part. A close topographic and temporal association between peripheral injury and onset of the movement disorders is crucial to diagnosing PIMD. PIMD is under-recognized and often misdiagnose...
Conference Paper
Background: A recently proposed “brain-first/body-first” dichotomy model of disease progression in Parkinson’s disease (PD) claims that Lewy body (LB) pathologies can begin either in the brain or in the body and progress in opposite rostro-caudal or caudal-rostral directions. Testing this model requires longitudinal follow-up of patients using obje...
Chapter
Movement Disorders in Psychiatry examines the complex interface between movement disorders and psychiatry, addressing both specific movement disorders in psychiatry, and behavioral syndromes associated with diseases categorized as movement disorders. After an overview of the clinical definitions and pathophysiology of movement disorders in Part 1,...
Chapter
Tourette syndrome (TS) is a childhood-onset complex neurobehavioral disorder. The defining feature of TS is the presence of tics, which are described as sudden-onset, recurrent, brief-lasting, irregular, involuntary movements (motor tics) or sounds (phonic tics). Most patients with TS also have a variety of comorbid behavioral disorders, particular...
Article
Purpose of the review: Orthostatic hypotension (OH) is the primary manifestation of cardiovascular autonomic dysfunction in Parkinson’s disease (PD) and can be a prodromal feature of the disease. We review the recent progress in the field of autonomic dysfunction in PD. Recent findings Individuals with isolated neurogenic OH should be followed up...
Article
BACKGROUND: There is definite evidence for the involvement of retina in Parkinson's disease (PD). However, a specific pattern has not been clear due to the cross-sectional nature of the majority of the previous studies. OBJECTIVE: The aim of this work was to study the pattern of changes in the retinal layers in patients with PD on longitudinal fol...
Article
INTRODUCTION: Levodopa is the most effective medication for the treatment of motor symptoms of Parkinson’s disease (PD). Several factors may affect the efficacy and tolerability of levodopa. These include the timing, dosage and administration of levodopa, concomitant drugs, food, PD-associated non motor symptoms, and various neurologic and non-neu...
Preprint
Full-text available
Background Psychotic symptoms occur in a majority of schizophrenia patients, and in approximately 50% of all Parkinson’s disease (PD) patients. Altered grey matter (GM) structure within several brain areas and networks may contribute to their pathogenesis. Little, however, is known about transdiagnostic similarities when psychotic symptoms occur in...
Article
Full-text available
Objectives To highlight the clinical significance of de novo dystonia and its spontaneous resolution during pregnancy. Methods Two patients were evaluated in a movement disorder clinic during their first trimester of pregnancy and followed up longitudinally. Results Our first patient developed severe right torticollis and laterocollis during the...
Article
Full-text available
Background A multimodal connectomic analysis using diffusion and functional MRI can provide complementary information on the structure–function network dynamics involved in complex neurodegenerative network disorders such as Parkinson’s disease (PD). Deep learning-based graph neural network models generate higher-level embeddings that could capture...
Article
Full-text available
Tacrolimus treatment is associated with a range of neurological adverse effects. Neurotoxicity caused by tacrolimus may result in subacute onset of tremor in a subset of patients. The commonly reported tremor phenomenology associated with tacrolimus neurotoxicity is the action tremor of bilateral upper limbs with or without rest tremor. Tremor may...
Article
Full-text available
BACKGROUND: There are few medications for the treatment of essential tremor (ET). One of these, primidone, which is one of only two front-line agents, is associated with considerable adverse drug reactions (ADRs). It is unclear why some primidone-treated ET patients develop ADRs whereas others do not, and why these ADRs seem to be more prevalent in...
Article
Full-text available
BACKGROUND: Task-specific dystonia (TSD) is a form of focal dystonia that occurs in the context of the performance of selective, highly-skilled, often repetitive, motor activity. TSD may be apparent during certain tasks such as writing, playing musical instruments, or other activities requiring fine motor control, but may also occur during certain...
Article
Purpose of the review To highlight five new things in the research and clinical aspects of essential tremor (ET). Recent findings The introduction of a new definition of ET and a new category “ET plus” were the major themes of the recent consensus statement. This new change demands a change in the approach to the clinical diagnosis of ET and relat...
Article
INTRODUCTION: Psychosis is one of the incapacitating non-motor symptoms of Parkinson’s disease (PD). Although several risk factors that include older age, rapid eye movement sleep (REM) behavior disorder (RBD), depression, and cognitive dysfunction have been identified, the exact neural correlates remain elusive. As cognitive impairment has a close...
Conference Paper
Background: After recovery from COVID-19, a substantial proportion of individuals with post-acute SARS-CoV2 (PASC) have persistent neurological problems that may include (1) fatigue, (2) ‘‘brain fog,’’ and (3) cardiovascular dysautonomia, manifested by excessive orthostatic tachycardia, lightheadedness, or a tendency to faint. We conducted comprehe...
Conference Paper
Background: Parkinson’s disease with orthostatic hypotension (PD+OH) can be difficult to distinguish clinically from the parkinsonian form of multiple system atrophy (MSA-P). Previous studies examined cardiac sympathetic neuroimaging to differentiate PD from MSA but without focusing specifically on PD+OH versus MSA-P, which often is the relevant di...
Article
Full-text available
Tremor is the most commonly encountered movement disorder in clinical practice. A wide range of pathologies may manifest with tremor either as a presenting or predominant symptom. Considering the marked etiological and phenomenological heterogeneity, it would be desirable to develop a classification of tremors that reflects their underlying pathoph...
Article
Full-text available
The synucleinopathies Parkinson's disease (PD), multiple system atrophy (MSA), and pure autonomic failure (PAF) are characterized by intra‐cytoplasmic deposition of the protein alpha‐synuclein and by catecholamine depletion. PAF, which manifests with neurogenic orthostatic hypotension (nOH) and no motor signs of central neurodegeneration, can evolv...
Article
A man in his early 60s with a medical history of granulomatosis with polyangiitis (GPA) in remission for two decades without maintenance therapy presented with non-specific complaints of profound fatigue and 40-pound weight loss. He was seronegative for antinuclear antibodies and cytoplasmic antineutrophilic antibodies, but erythrocyte sedimentatio...
Article
Full-text available
Objective Lewy body (LB) synucleinopathies such as Parkinson’s disease (PD) entail profound cardiac norepinephrine deficiency. The status of sympathetic noradrenergic innervation at other extracranial sites has been unclear. Although in vivo neuroimaging studies have indicated a cardioselective noradrenergic lesion, no previous study has surveyed p...
Article
Essential tremor (ET) is among the common movement disorders. A surge in research in recent years has considerably improved our understanding of disease etiology and pathogenesis, and its associated clinical phenomenology and natural history. With this progress have emerged a multitude of new questions and conundrums and newly proposed terminologie...
Article
Full-text available
Essential tremor (ET) is among the most prevalent neurological diseases. Appreciation in recent years of a richer tremor phenomenology, additional motor and non-motor features, variability in the natural course of tremor, associations with a host of other neurological conditions, and etiological and pathophysiological heterogeneity have resulted in...
Article
Full-text available
Essential tremor (ET) is among the most prevalent neurological diseases. Appreciation in recent years of a richer tremor phenomenology, additional motor and non-motor features, variability in the natural course of tremor, associations with a host of other neurological conditions, and etiological and pathophysiological heterogeneity have resulted in...
Article
Introduction: Handwriting is a complex activity involving cognitive, kinaesthetic and perceptual-motor components playing a critical role in the context of assessing neurodegenerative disorders. Difficulties in handwriting can be related to the disease and its severity which can serve as a prominent biomarker. This study proposes a methodology to m...
Article
Patients with Parkinson’s disease (PD) may undergo several elective and emergency surgeries. Motor fluctuations, presence of a wide range of non-motor symptoms, and the use of several medications, often not limited to dopaminergic agents, makes the perioperative management of PD challenging. However, the literature on perioperative management of PD...
Article
Sleep disturbance is one of the commonly reported non-motor symptoms in patients with Parkinson's disease (PD) as well as in Parkinson plus disorders such as multiple system atrophy (MSA), dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), and corticobasal syndrome (CBS). Although there is a wealth of literature on sleep disturb...
Article
Full-text available
Psychosis is a common and often debilitating non-motor symptom of Parkinson’s disease (PD). It typically manifests in the form of well-formed visual hallucinations and minor hallucinations, and, at times, can present with delusions and nonvisual hallucinations. Psychosis is associated with many adverse outcomes in PD, and for that reason, it is ess...
Chapter
Corticobasal degeneration is 1 of the atypical parkinsonian syndromes or Parkinsonism-plus syndromes that can mimic Parkinson disease, but it is distinct because of the added features of apraxia, dysphasia, cortical sensory signs, unusual dystonic postures, involuntary movements such as myoclonus, and “alien limb” sign. In this clinical article the...
Conference Paper
Objective: Psychosis is one of the debilitating non-motor symptom of Parkinson’s disease (PD) which commonly manifests through minor hallucinations (such as passage hallucinations, presence hallucinations, and illusions) and well-formed visual hallucinations. Cognitive impairment is strongly associated with psychosis in PD (PD-P). This study aimed...
Article
Abstract: OBJECTIVE: The objective of this study was to evaluate the gray matter (GM) volume alterations in different clinical stages of Parkinson’s disease (PD) through voxel-based morphometry (VBM). BACKGROUND: Assessment of the clinical stages of PD is usually carried out using the Hoehn and Yahr (H–Y) scale. However, there is paucity of litera...
Article
It is commonly thought that visuomotor adaptation is mediated by the cerebellum while reinforcement learning is mediated by the basal ganglia. In contrast to this strict dichotomy, we demonstrate a role for the basal ganglia in visuomotor adaptation (error‐based motor learning) in patients with Parkinson's disease (PD) by comparing the degree of mo...
Article
Background: West Nile virus (WNV) is a flavivirus that is recognized as one of the common causes of arboviral neurological disease in the world. WNV infections usually manifest with constitutional symptoms such as fever, fatigue, myalgia, rash, arthralgia, and headache. Neuroinvasive WNV infections are characterized by signs and symptoms suggestiv...
Article
Full-text available
Tremor is an involuntary, rhythmic, oscillatory movement of a body part. It is a central feature of a range of diseases resulting from pathological changes in the cerebellum. Interestingly, in modern times, the terms “cerebellar tremor” and “intention tremor” are often used synonymously and interchangeably. However, “cerebellar tremor” (i.e., tremo...
Article
Optical coherence tomography (OCT) has been evaluated as a tool to assess retinal changes in various neurodegenerative disorders. Parkinson’s disease (PD), is a neurodegenerative disorder wherein dopaminergic deficiency results in some of the symptoms. As retina also has high concentration of dopamine, it would be of interest for both the clinician...
Article
Introduction: Cervical dystonia is the most common focal dystonia encountered in a movement disorders clinic. It may have a huge impact on patients’ quality of life due to involuntary movement and abnormal posture of the head, neck pain, limitations in the range of neck movements, and psycho-social stress. Botulinum toxin is the preferred treatment...
Article
Full-text available
OBJECTIVES: To compare the sleep profiles of genetically proven cases of Huntington’s disease (HD) with healthy controls and to correlate the results of various sleep-related parameters with disease severity, duration, and length of cytosine–adenine–guanosine repeats. METHODS: This prospective study was conducted at the National Institute of Mental...
Preprint
Full-text available
It is commonly thought that visuomotor adaptation is mediated by the cerebellum while reinforcement learning is mediated by the basal ganglia. In contrast to this strict dichotomy, we demonstrate a role for the basal ganglia in visuomotor adaptation (error-based motor learning) in patients with Parkinsons disease (PD) by comparing the degree of mot...
Article
Objectives The present study was undertaken to evaluate the cognitive profile of Parkinson’s disease (PD) patients with REM sleep behavior disorder (RBD) and to correlate with the clinical stage and polysomnographic variables. Methods The study included 25 PD patients who had RBD and 25 PD patients who based on two questionnaires were determined a...
Article
Background: Essential tremor (ET) is reported to have a bimodal distribution of age at onset (AAO) with phenotypic variability based on the AAO. This study aims to explore the distribution of AAO based on mathematical modeling and ascertain the differences, if any, in the clinical features of groups. Methods: A chart review was conducted for 252...
Article
Tremor is a key clinical feature of several common neurological disorders. Adequate management of tremor has been an unmet need in clinical practice. Most of the anti-tremor medications have limited efficacy and are associated with undesirable adverse effects, especially in elderly patients. Several studies have reported good outcomes with the use...
Article
Full-text available
Patients with Parkinson’s disease (PD) develop a range of non-motor symptoms (NMS). Sleep disturbance is one of the common NMS of PD and the onset of sleep disorders often precede the onset of motor symptoms of PD. Motor symptoms of PD often receive the main clinical focus and the sleep disturbances often go unnoticed in clinical practice. Given th...
Article
Background: Freezing of gait (FOG) is a common and debilitating symptom in Parkinson's disease (PD); the pathogenesis and natural course of which has not been fully understood. Objectives: This study was performed to evaluate patients with FOG in PD and ascertain factors contributing to an early onset of FOG in patients with PD. Methodology: A char...
Article
Background Freezing of gait (FOG) is a common and debilitating symptom in Parkinson's disease (PD); the pathogenesis and natural course of which has not been fully understood. Objectives This study was performed to evaluate patients with FOG in PD and ascertain factors contributing to an early onset of FOG in patients with PD. Methodology A chart...
Article
Full-text available
Psychosis, manifested through formed visual hallucinations or minor hallucinations, is a common non-motor symptom of Parkinson’s disease (PD). The pathogenesis of psychosis in PD remains unclear; however, is possibly linked to structural and functional alterations in the hippocampus. To explore the role of hippocampus in psychosis, a detailed hippo...
Article
Improvement in motor symptoms with levodopa is one of the hallmark features of Parkinson’s disease (PD). The response to levodopa may reduce during the course of the illness. Few studies have also reported reduced response to levodopa in patients with PD several years after deep brain stimulation (DBS) of the subthalamic nucleus (STN) on both the s...
Article
Background: To investigate the diagnostic utility of signal intensity measurement of the substantia nigra pars compacta (SNc) using three dimensional (3D) neuromelanin-sensitive 31MRI, for discrimination of patients with PD from healthy controls. Methods: T1-weighted neuromelanin sensitive images of 16 patients with PD and 15 controls were quant...
Article
Background: Recent advances in neurophysiological techniques have contributed to our understanding of the pathophysiology of Huntington's disease (HD). Studies of the motor cortical excitability and central motor pathways have shown variable results. Objectives: Our aims were to evaluate the cortical excitability changes in HD using transcranial...
Article
Full-text available
Background: Orthostatic tremor (OT), a rare and complex movement disorder, is characterized by rapid tremor of both legs and the trunk while standing. These disappear while the patient is either lying down or walking. OT may be idiopathic/primary or it may coexist with several neurological conditions (secondary OT/OT plus). Primary OT remains an en...
Article
INTRODUCTION: Dystonia is one of the most prevalent forms of movement disorders and is characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. Dystonia causes significant morbidity with an adverse impact on the quality of life. When dystonia is medically refractory, causing se...
Article
Introduction Patients with Parkinson’s disease (PD) may develop several non-motor symptoms (NMS). Psychosis is one of the debilitating NMS of PD. The neurobiology of psychosis is not fully understood. This study aims to compare the frontal lobe functions of PD patients with and without psychosis using the Frontal Assessment Battery (FAB). Methodol...
Article
Full-text available
Background: Writer’s cramp (WC) is one of the commonly observed focal dystonias. The pathophysiology of WC has not been fully understood. The role of the cerebellum has been increasingly recognized in the pathogenesis of dystonia. As the cerebellum is crucial for maintaining accurate eye–hand coordination (EHC), its role in the pathogenesis of WC c...