Hand Knob Area of Premotor Cortex Represents the Whole Body in a Compositional Way.

Decades after the motor homunculus was first proposed, it is still unknown how different body parts are intermixed and interrelated in human motor cortical areas at single-neuron resolution. Using multi-unit recordings, we studied how face, head, arm, and leg movements are represented in the hand knob area of premotor cortex (precentral gyrus) in people with tetraplegia. Contrary to traditional expectations, we found strong representation of all movements and a partially "compositional" neural code that linked together all four limbs. The code consisted of (1) a limb-coding component representing the limb to be moved and (2) a movement-coding component where analogous movements from each limb (e.g., hand grasp and toe curl) were represented similarly. Compositional coding might facilitate skill transfer across limbs, and it provides a useful framework for thinking about how the motor system constructs movement. Finally, we leveraged these results to create a whole-body intracortical brain-computer interface that spreads targets across all limbs.

Hand knob sign in osmotic demyelinating syndrome.

BACKGROUND: Osmotic demyelinating syndrome, commonly recognized as a consequence of the rapid correction of hyponatremia, has been known to cause motor, neuropsychiatric, or extrapyramidal symptoms. We reported a patient with an unusual presentation involving bilateral hand weakness, and pseudobulbar affect. The imaging was compatible with osmotic demyelinating syndrome with bilateral hand knob lesions, despite no history of overcorrection of hyponatremia. CASE PRESENTATION: A 44-year-old female presented with three weeks of emotional lability, spastic dysarthria, and bilateral hand weakness following ankle surgery and a mild head injury. Physical examination revealed weakness in the intrinsic hand muscles, leading to a claw-like deformity of the hands, although sensation remained unimpaired. Magnetic resonance imaging (MRI) of the brain revealed several hyperintensities on fluid-attenuated inversion recovery imaging involving various areas, including the hand knob area of the bilateral precentral gyri, caudate, lentiform nuclei, and pons, suggestive of osmotic demyelinating syndrome. Clinical improvement was observed following a trial of intravenous pulse methylprednisolone and plasmapheresis. CONCLUSIONS: Bilateral hand weakness is an unusual manifestation of osmotic demyelinating syndrome. The precentral gyrus, specifically in the hand knob area, is the vulnerable region that can result from osmotic demyelinating syndrome.

A Narrative Review of Stroke of Cortical Hand Knob Area.

The cortical hand knob region of the brain is a knob-like segment of the precentral gyrus, projecting into the middle genu of the central sulcus. This anatomic landmark is responsible for intricate control of hand motor movements and has often been implicated in motor weakness following stroke. In some instances, damage to this area has been mistaken for peripheral causes of hand weakness. Our article aims to consolidate clinically relevant information on the cortical hand knob area in a comprehensive review to guide clinicians regarding diagnosis and treatment strategies. We conducted a systematic search within the Medline/PubMed database for reports of strokes in the cortical hand knob region. All studies were published electronically up until December 2023. The search was conducted using the keyword "hand knob". A total of 24 reports containing 150 patients were found. The mean and median ages were 65 and 67 years, respectively. Sixty-two percent of the individuals were male. According to the TOAST criteria for the classification of the stroke, 59 individuals had a stroke due to large-artery atherosclerosis, 8 had small-vessel occlusion, 20 had cardioembolism, 25 were determined, and 38 were undetermined. The most common etiologies for stroke in the hand knob area can be attributed to large vessel occlusions, small vessel occlusions, or cardioembolism. Presentations following damage to this area can mimic ulnar, median, or radial neuropathy as well. Our comprehensive review serves as a resource for recognizing and managing stroke in the cortical hand knob area.

Distinct Functional and Structural Connectivity of the Human Hand-Knob Supported by Intraoperative Findings.

Fine motor skills rely on the control of hand muscles exerted by a region of primary motor cortex (M1) that has been extensively investigated in monkeys. Although neuroimaging enables the exploration of this system also in humans, indirect measurements of brain activity prevent causal definitions of hand motor representations, which can be achieved using data obtained during brain mapping in tumor patients. High-frequency direct electrical stimulation delivered at rest (HF-DES-Rest) on the hand-knob region of the precentral gyrus has identified two sectors showing differences in cortical excitability. Using quantitative analysis of motor output elicited with HF DES-Rest, we characterized two sectors based on their excitability, higher in the posterior and lower in the anterior sector. We studied whether the different cortical excitability of these two regions reflected differences in functional connectivity (FC) and structural connectivity (SC). Using healthy adults from the Human Connectome Project (HCP), we computed FC and SC of the anterior and the posterior hand-knob sectors identified within a large cohort of patients. The comparison of FC of the two seeds showed that the anterior hand-knob, relative to the posterior hand-knob, showed stronger functional connections with a bilateral set of parietofrontal areas responsible for integrating perceptual and cognitive hand-related sensorimotor processes necessary for goal-related actions. This was reflected in different patterns of SC between the two sectors. Our results suggest that the human hand-knob is a functionally and structurally heterogeneous region organized along a motor-cognitive gradient.SIGNIFICANCE STATEMENT The capability to perform complex manipulative tasks is one of the major characteristics of primates and relies on the fine control of hand muscles exerted by a highly specialized region of the precentral gyrus, often termed the "hand-knob" sector. Using intraoperative brain mapping, we identify two hand-knob sectors (posterior and anterior) characterized by differences in cortical excitability. Based on resting-state functional connectivity (FC) and tractography in healthy subjects, we show that posterior and anterior hand-knob sectors differ in their functional connectivity (FC) and structural connectivity (SC) with frontoparietal regions. Thus, anteroposterior differences in cortical excitability are paralleled by differences in FC and SC that likely reflect a motor (posterior) to cognitive (anterior) organization of this cortical region.

Clinical features, etiology, and prognosis of hand knob stroke: a case series.

BACKGROUND: Hand knob stroke is a rare clinical disorder frequently misdiagnosed as peripheral neuropathy. The purpose of this study is to recognize this particular type of stroke by analyzing clinical features, etiology, and prognosis. METHODS: We enrolled 19 patients with acute hand knob stroke in the Department of Neurology of the Beijing Geriatric Hospital from January 2018 to January 2022, and the clinical and imaging data of the patients during hospitalization and follow-up were collected and summarized. RESULTS: Acute hand knob stroke accounted for 0.9% of all acute stroke, and ischemic stroke (17 cases, 89.5%) was more than hemorrhagic stroke (2 cases, 10.5%). All patients presented sudden contralateral hand paresis, 12 (63.2%) of them had only isolated hand paralysis, and the location of the lesion corresponded to different finger weakness. The cause of hand knob hemorrhage was hypertension, while the causes of hand knob infarction were mainly small-vessel occlusion (SVO) (35.3%) and large-artery atherosclerosis (LAA) (35.3%), and the rare causes include carotid artery dissection and carotid body tumor. After a median follow-up 13.5 months, the prognosis of 94.7% patients was good, and one patient (5.3%) had recurrent stroke. CONCLUSIONS: Hand knob stroke is a rare stroke with a good prognosis and a low stroke recurrence rate. Ischemic stroke is the predominant type and the main clinical manifestation is hand paresis. The cause of hand knob hemorrhage is hypertensive, while SVO and LAA are the main causes of hand knob infarction, but there are some rare etiologies.

A case report of isolated distal upper extremity weakness due to cerebral metastasis involving the hand knob area.

BACKGROUND: Unilateral weakness of an upper extremity is most frequently caused by traumatic nerve injury or compression neuropathy. In rare cases, lesion of the central nervous system may result in syndromes suggesting peripheral nerve damage by the initial examination. Pseudoperipheral hand palsy is the best known of these, most frequently caused by a small lesion in the contralateral motor cortex of the brain. The 'hand knob' area refers to a circumscribed region in the precentral gyrus of the posterior frontal lobe, the lesion of which leads to isolated weakness of the upper extremity mimicking peripheral nerve damage. The etiology of this rare syndrome is almost exclusively related to an embolic infarction. CASE PRESENTATION: We present the case of a 70-year-old male patient with isolated left sided upper extremity weakness and clumsiness without sensory disturbance suggesting a lesion of the radial nerve. Nerve conduction studies had normal results excluding peripheral nerve damage. Neuroimaging (cranial CT and MRI) detected 3 space occupying lesions, one of them in the right precentral gyrus. An irregularly shaped tumor was found by CT in the left lung with multiple associated lymph node conglomerates. The metastasis from this mucinous tubular adenocarcinoma with solid anaplastic parts to the 'hand knob' area was responsible for the first clinical sign related to the pulmonary malignancy. CONCLUSIONS: Pseudoperipheral palsy of the upper extremity is not necessarily the consequence of an embolic stroke. If nerve conduction studies have normal results, neuroimaging - preferably MRI - should be performed, as lesion in the hand-knob area of the precentral gyrus can also be caused by a malignancy.

New clinical characteristics and risk factors of hand knob infarction.

Hand knob infarction (HKI) is a rare clinical condition which is often misdiagnosed as peripheral neuropathy. This study aimed to identify the clinical characteristics and risk factors of HKI. Nine HKI patients admitted between January 2013 and March 2016 were confirmed by magnetic resonance imaging. Their medical records were collected and analyzed. The modified Rankin Scale was used to assess clinical outcomes. Routine laboratory tests, electrocardiogram, echocardiography, cranial magnetic resonance imaging, magnetic resonance angiography, computed tomography angiography, and Doppler ultrasonography examinations were performed. Seven patients had uniform involvement of all digits. One patient with radial weakness had a lesion in the lateral area of hand knob, and another patient with ulnar weakness had a lesion distributed in the medial area of hand knob. Hyperhomocysteinemia was a most common risk factor for HKI. Most HKI patients had a benign disease course, but three patients (33.33%) with the stroke type of large artery atherosclerosis had disease recurrence. We characterized clinical characteristics and risk factors of HKI which will help the diagnosis and management of HKI.

Cortical Hand Knob Stroke: Report of 25 Cases.

BACKGROUND: Although uncommon, cortical hand knob territory stroke is a well-defined stroke entity that mimics peripheral nerve damage. Atherosclerosis and hypertension are the most prevalent risk factors for the disease. Embolic origin, either artery-to-artery or cardioembolic, has been suggested as the most probable underlying mechanism. MATERIALS AND METHODS: Twenty-five patients with isolated hand palsy due to central origin were admitted to our department between 2006 and 2016. Cortical lesions were proven by either computed tomography or magnetic resonance imaging. RESULTS: The average age was 67 ± 12 years. Most of the cases were first-ever strokes (n = 23, 92%). Isolated infarct in the hand knob region was found in 18 of the 25 cases, whereas 7 had multiple acute infarctions. Supra-aortic atherosclerosis was found in 21 patients, 8 of them had 50% or greater ipsilateral stenosis of the internal carotid artery. Hypertension was the second most prevalent risk factor (n = 20, 80%). Quick improvement of symptoms was seen in almost every case (mean follow-up 17.5 months), 9 patients showed complete recovery, whereas 2 remained disabled and 1 died due to a malignant disease. Three patients suffered a recurrent stroke on follow-up. CONCLUSIONS: We conclude that distal arm paresis is a rare presentation of acute stroke with usually benign course.

Connectivity defines the distinctive anatomy and function of the hand-knob area.

Control of the hand muscles during fine digit movements requires a high level of sensorimotor integration, which relies on a complex network of cortical and subcortical hubs. The components of this network have been extensively studied in human and non-human primates, but discrepancies in the findings obtained from different mapping approaches are difficult to interpret. In this study, we defined the cortical and connectional components of the hand motor network in the same cohort of 20 healthy adults and 3 neurosurgical patients. We used multimodal structural magnetic resonance imaging (including T1-weighted imaging and diffusion tractography), as well as functional magnetic resonance imaging and navigated transcranial magnetic stimulation (nTMS). The motor map obtained from nTMS compared favourably with the one obtained from functional magnetic resonance imaging, both of which overlapped well within the 'hand-knob' region of the precentral gyrus and in an adjacent region of the postcentral gyrus. nTMS stimulation of the precentral and postcentral gyri led to motor-evoked potentials in the hand muscles in all participants, with more responses recorded from precentral stimulations. We also observed that precentral stimulations tended to produce motor-evoked potentials with shorter latencies and higher amplitudes than postcentral stimulations. Tractography showed that the region of maximum overlap between terminations of precentral-postcentral U-shaped association fibres and somatosensory projection tracts colocalizes with the functional motor maps. The relationships between the functional maps, and between them and the tract terminations, were replicated in the patient cohort. Three main conclusions can be drawn from our study. First, the hand-knob region is a reliable anatomical landmark for the functional localization of fine digit movements. Second, its distinctive shape is determined by the convergence of highly myelinated long projection fibres and short U-fibres. Third, the unique role of the hand-knob area is explained by its direct action on the spinal motoneurons and the access to high-order somatosensory information for the online control of fine movements. This network is more developed in the hand region compared to other body parts of the homunculus motor strip, and it may represent an important target for enhancing motor learning during early development.

Pseudoulnar palsy with concurrent wrist drop: case report.

Introduction and importance: Pseudoulnar palsy, characterized by weakness in the fourth and fifth digits, is a condition typically attributed to infarction of the medial aspect of the precentral gyrus's "hand knob." This anatomical site is located in the primary motor cortex of the brain, in the posterior lobe of the frontal cortex. This report presents a novel case of pseudoulnar nerve palsy in conjunction with wrist drop stemming from an infarction of the hand knob gyrus. Case presentation: A 78-year-old female with hypertension and hyperlipidemia experienced sudden right wrist weakness and impaired mobility in her fourth and fifth digits. Clinical examinations, including neuroimaging, supported the diagnosis of an infarction in the medial precentral gyrus. Brain MRI confirmed the diagnosis of an acute infarction in the medial precentral gyrus. The patient was treated with enoxaparin, aspirin, and dexamethasone, and was discharged after symptom improvement. Clinical discussion: Unlike the classical presentations, this case highlights the co-occurrence of ulnar and radial deficits following a unique infarction pattern. The distinct presentation of right pseudoulnar palsy with wrist drop was caused by an infarction at the level of the medial aspect of the hand knob. Conclusion: This case underscores the importance of considering the central causes of peripheral-like deficits, especially in older individuals with vascular risk factors, emphasizing the significance of early intervention in mitigating potential long-term consequences. This report contributes to the evolving understanding of central neurological presentations, and serves as a reminder of the need for a comprehensive diagnostic approach.

Hand Knob Syndrome Secondary to Ipsilateral Concomitant Carotid Fibromuscular Dysplasia and Proximal Atherosclerotic Disease.

One of the uncommon stroke presentations is the isolated wrist drop syndrome, caused by a stroke affecting the hand knob area, with the embolic mechanism being the most commonly identified mechanism. Here, we present the case of a 62-year-old female patient who presented with acute-onset isolated wrist drop secondary to right internal carotid artery fibromuscular dysplasia with a string of beads appearance and coexisting proximal atherosclerotic severe stenosis. The patient underwent successful carotid artery stenting. Patients with hand knob stroke may present a diagnostic dilemma and can be misdiagnosed as having peripheral neuropathy due to the absence of pyramidal signs and other symptoms of cortical involvement, leading to delayed or inappropriate treatment.

Repetitive facilitative exercise under continuous electrical stimulation for recovery of pure motor isolated hand palsy after infarction of the "hand knob" area: A case report.

PURPOSE: Pure motor isolated hand palsy (PMIHP) following infarction of the "hand knob" area is a rare entity in stroke. PMIHP usually recovers within the first few days, but there are rare cases where patients do not recover rapidly. Herein, we report a case of residual PMIHP in which repetitive facilitative exercise under concurrent low-amplitude continuous neuromuscular electrical stimulation ("RFE-under-cNMES") was introduced to improve hand function. CASE DESCRIPTION: A 65-year-old man with PMIHP (30 days after onset) participated in a rehabilitation program involving RFE-under-cNMES. This protocol followed an A1-B1-A2-B2 schedule, where the "A"-period consisted of RFE-under-cNMES ("A1," 2 weeks; "A2," 1 week), and the "B"-period consisted of 1-week conventional rehabilitation. OUTCOMES: The 5-week intervention promoted not only recovery from paralysis (8 points by the Fugl-Meyer Assessment), but also the ability to manipulate objects (13 points by the Action Research Arm test) and increased the subjective use of the affected upper limb during activities of daily living (2.88 points by the Motor Activity Log). Changes that exceeded the minimal clinically important difference occurred only in the RFE-under-cNMES period. CONCLUSIONS: The patient had improved outcomes. Further studies are required to determine the possibility of RFE-under-cNMES relieving motor paralysis in patients with PMIHP who do not recover rapidly.

Ischaemic Stroke of the "Hand-Knob" Area Due to Paradoxical Cerebral Air Embolism after Central Venous Catheterization-A Doubly Rare Occurrence: A Case Report and an Overview of Pathophysiology, Diagnosis, and Treatment.

Central venous catheters (CVCs) are increasingly used across specialties for invasive haemodynamic monitoring and for the delivery of fluids, medications, and nutritional support. Cerebral air embolism (CAE) is a rare but potentially fatal complication associated with the insertion, maintenance, and removal of CVCs. It can occur through different mechanisms, including the direct retrograde ascension of air into the cerebral veins and paradoxical embolism due to a right-to-left intracardiac or intrapulmonary shunt. The "hand-knob" area is the cortical region within the primary motor cortex that contains the representation of the hand. It is located in the superior precentral gyrus and is the site of less than 1% of all ischaemic strokes. We report here the case of a patient who experienced an ischaemic stroke of the right "hand-knob" area, due to paradoxical CAE through a previously undiagnosed patent foramen ovale (PFO), after the insertion of a catheter in the right internal jugular vein. We also provide an overview of the pathophysiology, diagnosis, and treatment of CAE. Suspecting CAE in the case of an acute neurological event occurring in close temporal relationship with central venous catheterization is paramount to allow the early recognition and treatment of this uncommon form of iatrogenic stroke.

Development and validation of a novel model based on hand knob score and white matter injury on MRI to predict hand function in children with cerebral palsy.

Background: Childhood hand function is considered to be one of the strongest predictors of the ability to participate in daily activities as children with cerebral palsy (CP) reach adulthood. The manual ability classification system (MACS) is currently the most widely used for grading hand function in children with CP. However, the MACS method is subjective and may be affected by the raters' experience. Hand knob is an important control center for hand movement. Therefor this study aimed to develop and validate an objective model for hand function estimation in children with CP and visualize it as a nomogram. Methods: A total of 70 Children (2-12 years old) with CP underwent magnetic resonance imaging (MRI) scanning, MACS assessment. According to MACS, children with CP were divided into mild impairment group (grade I-III) and severe impairment group (grade IV-V). Hand function prediction models based on (I) hand knob score, (II) clinical features, and (III) the combination of clinical features and hand knob score were developed and validated separately. The models were subjected to stepwise regression according to the maximum likelihood method, and the Akaike information criterion was used to select the best model. Model discrimination was assessed using receiver operating characteristic (ROC) and calibration curves. The nomogram was finally built according to the best model. Results: The area under the curve (AUC) of the hand knob score model in the training set was 0.752, the clinical features model was 0.819, and the hand knob score and clinical features combined model was 0.880. The AUC of the hand knob score model in the validation set was 0.765, the clinical features model was 0.782, and the combined model was 0.894. The best model was the hand knob score-clinical features combined model, and the nomogram finally incorporated two assessment items: the hand knob score and white matter injury. The estimated probability of hand function injury degree of the combined model displayed good agreement with the actual occurrence probability. Conclusions: The hand knob score-clinical features combined model can be used to preliminarily assess the degree of hand impairment in children with CP, with good calibration.

Pre-surgical fMRI Localization of the Hand Motor Cortex in Brain Tumors: Comparison Between Finger Tapping Task and a New Visual-Triggered Finger Movement Task.

Introduction: Pre-surgical mapping is clinically essential in the surgical management of brain tumors to preserve functions. A common technique to localize eloquent areas is functional magnetic resonance imaging (fMRI). In tumors involving the peri-rolandic regions, the finger tapping task (FTT) is typically administered to delineate the functional activation of hand-knob area. However, its selectivity may be limited. Thus, here, a novel cue-induced fMRI task was tested, the visual-triggered finger movement task (VFMT), aimed at eliciting a more accurate functional cortical mapping of the hand region as compared with FTT. Method: Twenty patients with glioma in the peri-rolandic regions underwent pre-operative mapping performing both FTT and VFMT. The fMRI data were analyzed for surgical procedures. When the craniotomy allowed to expose the motor cortex, the correspondence with intraoperative direct electrical stimulation (DES) was evaluated through sensitivity and specificity (mean sites = 11) calculated as percentage of true-positive and true-negative rates, respectively. Results: Both at group level and at single-subject level, differences among the tasks emerged in the functional representation of the hand-knob. Compared with FTT, VFMT showed a well-localized activation within the hand motor area and a less widespread activation in associative regions. Intraoperative DES confirmed the greater specificity (97%) and sensitivity (100%) of the VFMT in determining motor eloquent areas. Conclusion: The study provides a novel, external-triggered fMRI task for pre-surgical motor mapping. Compared with the traditional FTT, the new VFMT may have potential implications in clinical fMRI and surgical management due to its focal identification of the hand-knob region and good correspondence to intraoperative DES.

Optimal stimulation site for rTMS to improve motor function: Anatomical hand knob vs. hand motor hotspot.

Repetitive transcranial magnetic stimulation (rTMS) is used to modulate neuronal excitability of the human brain. Distant effects on contralateral corticomotor excitability can be exerted by interhemispheric modulation by low-frequency rTMS on ipsilateral hemisphere. To modulate corticospinal excitability, accurate determination of the stimulation site is important to maximize the effects of rTMS. In the present study, we investigated the difference in the distant effect of 1 Hz rTMS with respect to inducing functional improvement in the non-dominant hand by inhibiting the dominant hemisphere depending on cortical target areas. Ten healthy right-handed volunteers without any neurological disorders were enrolled. The anatomical hand knob (HK) identified from individual magnetic resonance imaging and the transcranial magnetic stimulation (TMS) induced hand motor hotspot (hMHS) by recording motor evoked potentials (MEPs) in the contralateral first dorsal interosseous muscle were determined. All participants underwent three conditions of 1 Hz rTMS on left hemisphere intervention; rTMS application over the HK, rTMS application over the hMHS, and sham-rTMS. Before and after each intervention, all participants undergone motor function assessments with their left hand. The cortical mapping showed that the hMHS was located anteriorly and laterally compared to the HK. Motor function tests showed the most significant improvements after the hMHS stimulation. When we compared the distant effects of target site on corticospinal excitability and motor behavior, delivering 1 Hz rTMS to the hMHS was more effective than delivering it to the HK for improving corticomotor excitability, motor skill, and dexterity. These results suggest that TMS-induced hMHS is an optimal target area to induce distant effect of low-frequency rTMS in motor function.

Comparison of hemodynamic changes after repetitive transcranial magnetic stimulation over the anatomical hand knob and hand motor hotspot: A functional near-infrared spectroscopy study.

BACKGROUND: Low-frequency rTMS can induce upregulation of excitability in the contralateral hemisphere by interhemispheric interaction. OBJECTIVE: The aim of this study was to compare the effects of interhemispheric modulation on hemodynamic changes after applying low-frequency rTMS over the anatomical hand knob (HK) and the hand motor hotspot (hMHS) in the dominant motor cortex. METHODS: Ten healthy right-handed participants without a history of neurological or psychiatric symptoms (five males; 29.8±2.8 years) participated in this single-blind, randomized, cross-over study. rTMS was applied under three conditions over the dominant (left) hemisphere for 20 minutes: 1) 1 Hz rTMS stimulation on the HK (HK-rTMS), 2) 1 Hz rTMS stimulation on the hMHS (hMHS-rTMS), and 3) sham stimulation (Sham-rTMS). For all participants, functional near-infrared spectroscopy (fNIRS) was applied for measurement of cerebral oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) concentration over the non-dominant (right) hemisphere during a serial reaction time task (SRTT) with the non-dominant (left) hand before and after each condition. RESULTS: The average coordinates of the hMHS (x = - 39.60 mm, y = - 17.11 mm, z = 66.40 mm) were anterior and lateral to the HK (x = - 36.72 mm, y = - 28.87 mm, z = 56.41 mm). In fNIRS time-series analysis, the integral value of oxyHb wassignificantly increased over the motor cortical region of the non-dominant hemisphere after the hMHS-rTMS compared with Sham-rTMS. The HK-rTMS also showed slight increment of oxyHb concentration but without statistical significance. The SPM group analysis showed greater magnitude of the activity in hMHS-rTMS than that of HK-rTMS after stimulation (p < 0.05). CONCLUSIONS: These results demonstrated an interhemispheric modulation effect of hemodynamic changes by 1 Hz rTMS. The hMHS produced a more robust modulation effect of 1 Hz rTMS on the contralateral hemisphere than did the HK. Therefore, the rTMS can be considered a better stimulation target than the HK.

Selective Hand Motor Cortex Lesions Masquerading as "Pseudoperipheral Nerve Palsy".

Strategic cortical lesions involving the hand motor cortex (HMC) presenting acutely as distal upper limb pure motor weakness certainly do need to be differentiated on clinical grounds from "pseudoperipheral palsy." This rare phenotype can imitate peripheral motor nerve deficits and should not be easily overlooked. The isolated "central hand and finger weakness" presenting as an acute onset of varying combinations such as pseudomedian, pseudoradial, and/or pseudoulnar nerve palsy is intriguing to the novice. In literature, this phenotype has been reported solely to result from cortical cerebral infarction and documented to occur in <1% of all ischemic strokes. The apropos of six "unforgettable patients" here highlights the heterogeneous pathophysiologic etiologies and mechanisms that included not only the conventional stroke risk factors but also hyperhomocysteinemia, common carotid artery thrombosis due to hyperhomocysteinemia and severe iron-deficiency anemia, biopsy-proven giant cell arteritis (GCA), cerebral metastasis, and dilated cardiomyopathy-related left ventricular thrombosis. Physicians and neurologists alike, as clinicians, need to be familiar with the peculiarities and clinical presentations of central hand control network cortical lesions.

Morphometry of the Hand Knob Region and Motor Function Change in Eloquent Area Glioma Patients.

PURPOSE: The hand knob area is the cortical representation of motor hand function. The current study aimed to investigate the effects of eloquent area gliomas on the morphometry of the hand motor cortex and preoperative hand motor function. METHODS: A retrospective study of 320 glioma patients was conducted. Seventy-eight patients with gliomas involving motor functional area were finally enrolled. Using axial T2-weight magnetic resonance images, the width and height of the hand knob were measured in both hemispheres, and differences were compared between the affected and unaffected hemispheres. Receiver operating characteristic (ROC) curve and logistic regression analysis were used to estimate the degree of correlation between distance measurements and motor impairment. RESULTS: The width and height of the hand knob in the affected and unaffected hemispheres were significantly different (p < 0.0001). The width, height and distance from the tumor to hand knob were reduced in the functionally impaired group compared to the unimpaired group (p = 0.0003, p < 0.0001, p = 0.0005, respectively). The three parameters were significantly correlated and remained significant in ROC and logistic regression analysis. The optimal cut-off value of width, height and distance for identifying preoperative hand muscle strength were 5.73 mm, 5.80 mm and 5.92 mm, respectively. CONCLUSION: The morphometry of the hand knob is often changed by the infiltration or extrusion of the tumors that were located in or near the hand knob. The width, height of hand knob and the distance from tumor to hand knob could serve as anatomic biomarkers related to preoperative neurological motor deficits.

Ischemic stroke of the "hand knob area": A case series and literature review.

Isolated hand paresis may reflect an infarction of the "hand knob area", which represents less than 1% of all ischemic strokes. In this type of stroke, a potential source of embolism is often identified. There are no large case series regarding this topic in Latin America. Herein we present the largest cohort of this entity in the region and we compare our results with those previously published. We analyzed all stroke patients admitted to our hospital between May 2015 - June 2018. Only patients with motor +/- sensory deficits restricted to the hand and ischemic stroke confirmed by MRI were included. We assessed stroke mechanism, clinical characteristics and outcome. From 339 patients admitted with ischemic stroke, 12 (3.53%) were included (9 men, 75%). Mean age: 60.4 years-old (range:24-79). Localization of stroke: 8 patients (66%) precentral gyrus, 3 (25%) postcentral; in 1 both gyri were affected. Stroke mechanism according to TOAST classification was as follows: two patients (16%) large artery atherosclerosis, two cardioembolic, one other determined etiology (thrombophilia), seven (58%) undetermined etiology (SUE). Nine patients (75%) received antiplatelets and statins, and three (25%) anticoagulants. The mean follow-up period was 11 months (range 1-26). Stroke recurrence was observed in one patient. At follow up, eight patients (66%) had a modified Rankin Score (mRS) of 0 and one a mRS of 1. In conclusion, in this series the most prevalent stroke mechanism was SUE, mainly embolic stroke of undetermined source. The outcome was excellent regardless of stroke mechanism.