Alexander Lin

Brigham and Women's Hospital | BWH · Department of Radiology

Soccer is played by more than 250 million people worldwide. Repeatedly heading the ball may place soccer players at high risk for repetitive subconcussive head impacts (RSHI). This study evaluates the long-term effects of RSHI on neurochemistry in athletes without a history of clinically diagnosed concussion, but with a high exposure to RSHI. Eleve...

The goal was to identify which neurochemicals differ in professional athletes with repetitive brain trauma (RBT) when compared to healthy controls using a relatively new technology, in vivo Localized COrrelated SpectroscopY (L-COSY). To achieve this, L-COSY was used to examine five former professional male athletes with 11 to 28 years of exposure t...

Traumatic brain injury results in a metabolic cascade of changes that occur at the molecular level, invisible to conventional imaging methods such as computed tomography or magnetic resonance imaging. Non-invasive metabolic imaging tools such as single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic res...

Background Clinically meaningful cognitive impairment has typically been defined as a single impaired test score, but this approach is prone to false‐positive errors. Examining two test scores at a lower threshold (i.e., using neuropsychological criteria) can improve diagnostic reliability and has shown stronger associations with biomarkers of Alzh...

Purpose Women exposed to intimate partner violence (IPV) may experience head, neck, and facial trauma, increasing their risk for concomitant brain injury (BI). The study of IPV-BI poses unique challenges due to safety, demographic, biological, and social factors, requiring considerations beyond the commonly used methods employed in BI research. Thu...

Objective Exposure to repetitive head impacts (RHI) has been linked to Chronic Traumatic Encephalopathy (CTE) and neuropathological alterations such as white matter shear injuries. In this study, we use diffusion-tensor imaging (DTI) to investigate in vivo white matter alterations among former American football players. We also investigate how age...

Background and Objectives Exposure to repetitive head impacts (RHI) is linked to the development of chronic traumatic encephalopathy (CTE), which can only be diagnosed at post-mortem. The presence of a cavum septum pellucidum (CSP) is a common finding in post-mortem studies of confirmed CTE and in neuroimaging studies of individuals exposed to RHI....

Importance Exposure to repetitive head impacts (RHI) is associated with increased risk for neurodegeneration. Accumulation of toxic proteins due to impaired brain clearance is suspected to play a role. Objective To investigate whether perivascular space (PVS) volume is associated with lifetime exposure to RHI in individuals at risk for RHI-associa...

Background Androgen deprivation therapy (ADT) in prostate cancer (PCa) has been associated with development of insulin resistance. However, the predominant site of insulin resistance remains unclear. Methods The ADT & Metabolism Study was a single‐center, 24‐week, prospective observational study that enrolled ADT‐naive men without diabetes who wer...

Exposure to repetitive head impacts (RHIs) in contact sports is associated with neurodegenerative disorders including chronic traumatic encephalopathy (CTE) which currently can be diagnosed only at postmortem. American football players are at higher risk of developing CTE given their exposure to RHIs. One promising approach for diagnosing CTE in vi...

Background Traumatic encephalopathy syndrome (TES) is defined as the clinical manifestation of the neuropathological entity chronic traumatic encephalopathy (CTE). A core feature of TES is neurobehavioral dysregulation (NBD), a neuropsychiatric syndrome in repetitive head impact (RHI)-exposed individuals, characterized by a poor regulation of emoti...

Background Repetitive head impacts (RHI) from American football can lead to tau and non‐tau pathologies that might present as white matter hyperintensities (WMH) on FLAIR MRI. In 2022, we published a study in Alzheimer’s & Dementia that examined WMH and their association with risk factors and clinical function in former elite football players. That...

Objective White matter hyperintensity (WMH) burden is greater, has a frontal-temporal distribution, and is associated with proxies of exposure to repetitive head impacts (RHI) in former American football players. These findings suggest that in the context of RHI, WMH might have unique etiologies that extend beyond those of vascular risk factors and...

Background and Objectives Recent data link exposure to repetitive head impacts (RHIs) from American football with increased white matter hyperintensity (WMH) burden. WMH might have unique characteristics in the context of RHI beyond vascular risk and normal aging processes. We evaluated biological correlates of WMH in former American football playe...

The acute state of anorexia nervosa (AN) is associated with widespread reductions in cortical gray matter (GM) thickness and white matter (WM) volume, suspected changes in myelin content and elevated levels of the neuronal damage marker neurofilament light (NF-L), but the underlying mechanisms remain largely unclear. To gain a deeper understanding...

Oxidative stress, an imbalance between the production of reactive oxygen species and available antioxidant capacity, is implicated in multiple psychiatric disorders and neurodegenerative conditions. Peripheral and preclinical studies suggest oxidative stress differs by biological sex and covaries with estrogens. However, limited knowledge exists on...

Sport-related concussion (SRC) affects an estimated 1.6 to 3.8 million Americans each year. Sport-related concussion results from biomechanical forces to the head or neck that lead to a broad range of neurologic symptoms and impaired cognitive function. Although most individuals recover within weeks, some develop chronic symptoms. The heterogeneity...

The aim of this guideline is to provide a series of evidence-based recommendations that allow those new to using MEGA-PRESS to produce high-quality data for the measurement of GABA levels using edited magnetic resonance spectroscopy with the MEGA-PRESS sequence at 3T. GABA is the main inhibitory neurotransmitter of the central nervous system and ha...

Context: Nicotinamide adenine dinucleotide (NAD) levels decline with aging and age-related decline in NAD has been postulated to contribute to age-related diseases. Objective: We evaluated the safety and physiologic effects of NAD augmentation by administering its precursor, β-nicotinamide mononucleotide (MIB-626, Metro International Biotech, Wo...

Magnetic resonance spectroscopy is a powerful, non-invasive, quantitative imaging technique that allows for the measurement of brain metabolites that has demonstrated utility in diagnosing and characterizing a broad range of neurological diseases. Its impact, however, has been limited due to small sample sizes and methodological variability in addi...

Background Patterns of cognitive impairment in former American football players are uncertain because objective neuropsychological data are lacking. This study characterized the neuropsychological test performance of former college and professional football players. Methods One hundred seventy male former football players ( n =111 professional, n...

Background and purpose: The purpose was to explore the effects of transcutaneous trigeminal nerve stimulation (TNS) on neurochemical concentrations (brainstem, anterior cingulate cortex [ACC], dorsolateral prefrontal cortex [DLPFC], ventromedial prefrontal cortex [VMPFC], and the posterior cingulate cortex [PCC]) using ultrahigh-field magnetic res...

Neurological soft signs (NSS) are minor deviations in motor performance. During childhood and adolescence, NSS are examined for functional motor phenotyping to describe development, to screen for comorbidities, and to identify developmental vulnerabilities. Here, we investigate underlying brain structure alterations in association with NSS in physi...

Background and Aims: Intermittent claudication (IC) in patients with peripheral artery disease (PAD) is thought to be caused by reduced lower extremity macrovascular blood flow. However, the ankle-brachial index (ABI) (a macrovascular measure) does not correlate well with patient-reported outcome measures. We aimed to study microvascular and metabo...

Brain iron is central to dopaminergic neurotransmission, a key component in schizophrenia pathology. Iron can also generate oxidative stress, which is one proposed mechanism for gray matter volume reduction in schizophrenia. The role of brain iron in schizophrenia and its potential link to oxidative stress has not been previously examined. In this...

Purpose: Flourine-18-flortaucipir tau positron emission tomography (PET) was developed for the detection for Alzheimer's disease. Human imaging studies have begun to investigate its use in chronic traumatic encephalopathy (CTE). Flortaucipir-PET to autopsy correlation studies in CTE are needed for diagnostic validation. We examined the association...

Introduction: The presentation, risk factors, and etiologies of white matter hyperintensities (WMH) in people exposed to repetitive head impacts are unknown. We examined the burden and distribution of WMH, and their association with years of play, age of first exposure, and clinical function in former American football players. Methods: A total...

Stress exposures and dysregulated responses to stress are implicated in psychiatric disorders of mood, anxiety, and cognition. Perceived stress, an individual's appraisal of experienced stress and ability for coping, relates to dysregulated functioning in resting state brain networks. Alterations in GABAergic function may underlie perceived stress-...

Repetitive head impacts (RHI) are common in youth athletes participating in contact sports. RHI differ from concussions; they are considered hits to the head that usually do not result in acute symptoms and are therefore also referred to as “subconcussive” head impacts. RHI occur e.g., when heading the ball or during contact with another player. Ev...

Objective To correlate brain metabolites to clinical outcome using magnetic resonance spectroscopy (MRS) in patients undergoing targeted temperature management (TTM) after cardiac arrest, and assess their relationships to MRI and EEG variables. Methods A prospective cohort of 50 patients was studied. The primary outcome was coma recovery to follow...

Background Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that has been neuropathologically diagnosed in brain donors exposed to repetitive head impacts, including boxers and American football, soccer, ice hockey, and rugby players. CTE cannot yet be diagnosed during life. In December 2015, the National Institute of Neurologi...

Background: Repetitive head impacts (RHI) from contact sports have been associated with cognitive and neuropsychiatric disorders. However, not all individuals exposed to RHI develop such disorders. This may be explained by the reserve hypothesis. It remains unclear if the reserve hypothesis accounts for the heterogenous symptom presentation in RHI...

Background Exposure to repetitive head impacts (RHI) is associated with an increased risk of later-life neurobehavioral dysregulation and neurodegenerative disease. The underlying pathomechanisms are largely unknown. Purpose To investigate whether RHI exposure is associated with later-life corpus callosum (CC) microstructure and whether CC microstr...

Adult-onset non-cirrhotic hyperammonemia (NCH) is a rare, but often fatal condition that can result in both reversible and irreversible neurological defects. Here we present five cases of adult-onset non-cirrhotic hyperammonemia wherein brain magnetic resonance spectroscopy (MRS) scans for cerebral glutamine (Gln) and myo-inositol (mI) levels helpe...

Objective: We describe magnetic resonance spectroscopy (MRS) changes in comatose patients undergoing targeted temperature management (TTM) after cardiac arrest, and their relationships to relevant clinical, MRI, and EEG variables. Methods A prospective cohort of 50 patients was studied. The primary outcome was coma recovery to follow commands. Comp...

Sport-related brain injury is very common, and the potential long-term effects include a wide range of neurological and psychiatric symptoms, and potentially neurodegeneration. Around the globe, researchers are conducting neuroimaging studies on primarily homogenous samples of athletes. However, neuroimaging studies are expensive and time consuming...

Proton (1H) magnetic resonance spectroscopy provides a non-invasive and quantitative measure of brain metabolites. Traumatic brain injury impacts cerebral metabolism and a number of research groups have successfully used this technique as a biomarker of injury and/or outcome in both pediatric and adult TBI populations. However, this technique is un...

Intimate partner violence includes psychological aggression, physical violence, sexual violence, and stalking from a current or former intimate partner. Past research suggests that exposure to intimate partner violence can impact cognitive and psychological functioning, as well as neurological outcomes. These seem to be compounded in those who suff...

Traumatic brain injuries (TBIs) are common with an estimated 27.1 million cases per year. Approximately 80% of TBIs are categorized as mild TBI (mTBI) based on initial symptom presentation. While in most individuals, symptoms resolve within days to weeks, in some, symptoms become chronic. Advanced neuroimaging has the potential to characterize brai...

Younger age at first exposure (AFE) to repetitive head impacts while playing American football increases the risk for later-life neuropsychological symptoms and brain alterations. However, it is not known whether AFE is associated with cortical thickness in American football players. Sixty-three former professional National Football League players...

Purpose: MR spectroscopy of dynamic systems is limited by low signal to noise. Denoising along a series of acquired spec- tra exploits their temporal correlation to improve the quality of individual spectra, and reduce errors in fitting metabolite peaks. In this study we compare the performance of several denoising methods. Methods: Six different d...

Succinic semialdehyde dehydrogenase (SSADH) deficiency is an autosomal recessive disorder of γ-aminobutyric acid (GABA) degradation, resulting in elevations of brain GABA and γ-hydroxybutyric acid (GHB). Previous magnetic resonance (MR) spectroscopy studies have shown increased levels of Glx in SSADH deficiency patients. Here in this work, we measu...

The translation of MRS to clinical practice has been impeded by the lack of technical standardization. There are multiple methods of acquisition, post-processing, and analysis whose details greatly impact the interpretation of the results. These details are often not fully reported, making it difficult to assess MRS studies on a standardized basis....

Proton magnetic resonance spectroscopy (¹H MRS) has become the method of choice to investigate brain chemical abnormalities, especially in psychiatric diseases. In this chapter, we will cover a few brain metabolites that can be reliably measured with MRS method, namely, N‐acetylaspartate (NAA), glutamate (Glu), glutamine (Gln), gamma‐aminobutyric a...

The long-term neurologic consequences of exposure to repetitive head impacts (RHI) are not well understood. This study used magnetic resonance spectroscopy (MRS) to examine later-life neurochemistry and its association with RHI and clinical function in former National Football League (NFL) players. The sample included 77 symptomatic former NFL play...

Objective: To evaluate the strength of associations between single-task and dual-task gait measures and posterior cingulate gyrus (PCG) neurochemicals in acutely concussed collegiate athletes. Setting: Participants were recruited from an NCAA Division 1 University. Participants: Nineteen collegiate athletes acutely (<4 days) following sports-r...

Sports‐related concussion is a serious health challenge, and females are at higher risk of sustaining a sports‐related concussion compared to males. Although there are many studies that investigate outcomes following concussion, females remain an understudied population, despite representing a large proportion of the organized sports community. In...

Traumatic brain injury (TBI) is a major cause of disability worldwide, but the heterogeneous nature of TBI with respect to injury severity and health comorbidities make patient outcome difficult to predict. Injury severity accounts for only some of this variance, and a wide range of preinjury, injury‐related, and postinjury factors may influence ou...

Sports-related brain injury is very common, and the potential long-term effects include a widerange of neurological and psychiatric symptoms, and potentially neurodegeneration. Aroundthe globe, researchers are conducting neuroimaging studies on primarily homogenoussamples of athletes. However, neuroimaging studies are expensive and time consuming,...

Magnetic Resonance Spectroscopy (MRS) is a non-invasive technique that quantitatively measures the metabolic composition of tissues in vivo using conventional magnetic resonance (MR) scanners. This technology is of special interest for clinical applications in psychiatry due to its non-invasive nature. In recent years, studies have demonstrated its...

Purpose: Few studies have investigated recovery between sexes using objective outcome measures. Our purpose was to examine the independent association between biological sex and recovery of post-concussion gait among collegiate athletes. Methods: We evaluated participants with a diagnosed concussion <7 days post-injury, and approximately 1.5 mon...

Background Factors of increased prevalence among individuals with Black racial identity (e.g., cardiovascular disease, CVD) may influence the association between exposure to repetitive head impacts (RHI) from American football and later-life neurological outcomes. Here, we tested the interaction between racial identity and RHI on neurobehavioral ou...

BACKGROUND Ivosidenib (AG-120, IVO) is a first-in-class oral inhibitor of mutant isocitrate dehydrogenase 1 (mIDH1), and vorasidenib (AG-881, VOR) is an oral, potent, brain-penetrant inhibitor of mIDH1/2. Both have been evaluated in glioma patients in ongoing phase 1 studies. In orthotopic glioma models, IVO and VOR reduced 2-hydroxyglutarate (2-HG...

Intimate partner violence includes psychological aggression, physical violence, sexual violence, and stalking from a current or former intimate partner. Experiencing intimate partner violence is associated with impaired neurocognitive and psychosocial functioning, mental illness, as well as structural brain alterations. These impairments seem to be...

Proton magnetic resonance spectroscopy provides a non-invasive and quantitative measure of brain metabolites. Traumatic brain injury impacts cerebral metabolism and a number of research groups have successfully used this technique as a biomarker of injury and/or outcome in both pediatric and adult TBI populations. However, this technique is underut...

Intimate partner violence includes psychological aggression, physical violence, sexual violence, and stalking from a current or former intimate partner. Experiencing intimate partner violence is associated with impaired neurocognitive and psychosocial functioning, mental illness, as well as structural brain alterations. These impairments seem to be...

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to repetitive head impacts. CTE has been linked to disruptions in cognition, mood, and behavior. Unfortunately, the diagnosis of CTE can only be made post-mortem. Neuropathological evidence suggests limbic structures may provide an opportunity to characte...

Proton MRS (¹H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption ha...

Mutations in isocitrate dehydrogenase (mIDH) are common in lower-grade glioma (LGG; mIDH1, 80%; mIDH2, 4%) and lead to epigenetic and genetic changes that promote oncogenesis via production of the oncometabolite 2-hydroxyglutarate (2-HG). AG-120 (ivosidenib) is a first-in-class oral mIDH1 inhibitor associated with a favorable safety profile in an o...

Background: Previous research has shown evidence for transient neuronal loss after repetitive head impacts (RHI) as demonstrated by a decrease in N-acetylaspartate (NAA). However, few studies have investigated other neuro-metabolites that may be altered in the presence of RHI; furthermore, the relationship of neuro-metabolite changes to neurocognit...

Background: Despite the widespread adoption of targeted temperature management (TTM), coma after cardiac arrest remains a common problem with a high proportion of patients suffering substantial disability. Prognostication after cardiac arrest, particularly the identification of patients with likely good outcome, remains difficult. Methods: We pe...

Context Plasma betaine correlates with insulin sensitivity in humans. Betaine supplementation in high-fat fed mice improves glucose homeostasis, hepatic fat, insulin sensitivity, and increases energy expenditure and oxidative capacity of inguinal white adipose tissue. Objective To assess metabolic effects of oral betaine in obese participants with...

BACKGROUND AND PURPOSE Tai Chi is a mind‐body exercise that has been shown to improve both mental and physical health. As a result, recent literature suggests the use of Tai Chi to treat both physical and psychological disorders. However, the underlying physiological changes have not been characterized. The aim of this pilot study is to assess the...