[Clinical examination of spatial neglect and other disorders of spatial cognition]. / Klinische Untersuchung des unilateralen Neglects und weiterer Störungen der Raumkognition.

Neglect occurring after stroke, neoplasms or degenerative processes can lead to considerable disability in everyday life as can other disorders of spatial orientation. Therefore, a dedicated examination and early diagnostic classification are obligatory. Behavioral tests are helpful in this respect, enabling the clinician to obtain an initial overview of the existing deficits even at the patient's bedside. The clinical (bedside) examination of spatial neglect as well as the corresponding differential diagnostic procedure for the clarification of (possibly additionally or exclusively existing) hemianopia and extinction, as well as the examination of disorders of visuospatial perception, visuoconstructive disorders, topographic disorders, Bálint's syndrome, simultanagnosia, and optic ataxia are presented. The presentation is based on the newly revised (year 2023) guidelines of the Association of the Scientific Medical Societies in Germany (AWMF) on this subject area.

Hemisensory syndrome: Hyperacute symptom onset and age differentiates ischemic stroke from other aetiologies.

BACKGROUND: An important cause of hemisensory syndrome is ischemic stroke. However, the diagnostic yield of neuroradiological imaging on hemisensory syndrome is low. Therefore, we aim to describe patients hospitalized with isolated hemisensory syndrome, and to identify clinical features associated with an aetiology of ischemic stroke. METHODS: We performed a single centre retrospective observation study, identifying patients who were hospitalised with hemisensory syndrome from October 2015 to March 2016, and whom underwent a magnetic resonance imaging (MRI) brain during the admission. Ischemic stroke was defined as the presence of restricted diffusion-weighted image on the MRI brain. Clinical information was analysed and compared between patients with and without stroke seen on MRI brain. RESULTS: 79 patients, 36 (45.6%) males and 43 (54.4%) females, aged between 30 to 87 years (mean 54), were included in the final analysis. 18 (22.8%) patients were identified to have an acute ischemic stroke. Clinical features associated with ischemic stroke in hospitalised patients with hemisensory syndrome include symptom onset of ≤24 h at presentation (odds ratio 31.4, 95% CI 3.89-254.4), advanced age (odds ratio 1.14, CI 1.05-1.25) and smoking (odds ratio 7.35, 95% CI 1.20-45). CONCLUSION: Older patients, with a history of smoking, and who present with an acute onset of symptoms, are more likely to have ischemic stroke as the cause of their hemisensory syndrome.

Interdisciplinary approach to the treatment of rare visual illusions in a veteran.

Upside-down reversal of vision (UDRV) is a rare form of metamorphopsia, or visual illusions that can distort the size, shape or inclination of objects. This phenomenon is paroxysmal and transient in nature, with patients reporting a sudden inversion of vision in the coronal plane, which typically remains for seconds or minutes, though occasionally persists for hours or days, before returning to normal. Distorted egocentric orientation (ie, the patient perceives the body to be tilted away from the vertical plane) is even more rare as a co-occurring phenomenon. To the best of our knowledge, this is the first reported case of a veteran who presented with UDRV and distorted egocentric orientation during hospitalisation on an inpatient physical medicine and rehabilitation setting following an elective hip surgery. This case serves not only to document the presence of rare visual illusions, but also illustrates the importance and value of an interdisciplinary team approach.

Validation of a simple screening test for elementary visuo-spatial perception deficit.

OBJECTIVE: The reliability and validity of a screening test for a deficit in elementary visuo-spatial perception (EVSP) were evaluated. METHOD: This prospective study collected performance from 210 typically developing individuals and evaluated the internal consistency of the EVSP screening test. Test-retest reliability was examined with 25 individuals. Validity also involved retrospective clinical data collected from 223 non-typically developing children coming to the hospital for outpatient consultation. Since EVSP matures through childhood, we standardized the EVSP screening test scores by age category and performed Pearson correlations with standardized clinical tests scores. RESULTS: Test-retest reliability (intraclass correlation coefficient=0.76) and internal consistency (Cronbach's alpha=0.76) were satisfactory. Construct validity included correlation with the subtests of the Wechsler Intelligence Scale IV (WISC-IV) involving visuo-spatial analysis (Matrix Reasoning and Block Design, P<0.01; Symbol Search and Coding, P<0.05) and was reinforced by the expected non-correlation between the Verbal Comprehension Index and EVSP scoring class. The EVSP scoring class was correlated with Manual dexterity of the M-ABC (P<0.05) and the Working Memory Index (P<0.05) of the WISC-IV including the subtest Arithmetic (P<0.01). CONCLUSION: This screening test is reliable and valid to evaluate EVSP before more complex cognitive or motor assessment.

Visual perceptual skills and visual motor integration in children and adolescents after allogeneic hematopoietic stem cell transplantation.

The aim of the study was to study visual acuity, visual perceptual, and VMI skills in patients after HSCT in childhood. Tests of visual perceptual skills, VMI, and visual acuity were performed in 102 children/adolescents (age range 4.3-20.9 years). Mean time from HSCT to testing was 6.0 years (0.9-17.5 years). Visual acuity was median 1.0 decimal (range 0.16-1.6). Visual perceptual skills (memory, form constancy, visual sequential memory) and VMI were low compared to age-equivalent normative data with, respectively, 36%, 45%, 60%, and 46% of all patients performing below the 25 percentile. All patients performed significantly lower than the 50 percentile in the reference material in visual sequential memory, P < .001 (boys P < .001 and girls P < .05). All patients also performed significantly lower than the 50 percentile in VMI (P < .01) (boys P < .05). Pretransplant conditioning regimen did not affect outcome if the results were corrected for age at HSCT. Visual perceptual skill problems and VMI problems frequently occur in patients after HSCT in childhood. Age at HSCT and original diagnosis influence the outcome. Neuropsychological assessment including visual perception is recommended in children after HSCT.

Cognitive map recall test: A new specific test to assess topographical disorientation.

Topographical disorientation, the inability to orient in a well-known environment, is a very incapacitating syndrome. Despite its relatively high frequency after a right cerebral lesion, there is currently no specific neuropsychological test to assess it. We propose a completely new test, with preliminary normative data, assessing the subjects' ability to recall allocentric spatial information from their cognitive map. The subjects are asked to mentally compare distances and directions between landmarks in their familiar environment. This necessitates creating an individual version of the test tailored to every participant's knowledge. This task was proposed to 53 patients with a right lesion and a control group (N = 133). We evaluated performance at comparing distances and directions, and the impact of sociodemographic variables (age, gender, and education). Results show that a right cerebral lesion leads to difficulties in evoking and comparing allocentric spatial information, and more specifically in judging directions. Furthermore, the results show an impact of age, but not gender nor education, on recalling information from a cognitive map. Although there are some intrinsic difficulties (for example in creating patient-specific versions of the test), preliminary normative data indicate that this original test is workable and provides important information in assessing topographical disorientation in clinical practice.

Stroke vision, aphasia, neglect (VAN) assessment-a novel emergent large vessel occlusion screening tool: pilot study and comparison with current clinical severity indices.

BACKGROUND: Identification of emergent large vessel occlusion (ELVO) stroke has become increasingly important with the recent publications of favorable acute stroke thrombectomy trials. Multiple screening tools exist but the length of the examination and the false positive rate range from good to adequate. A screening tool was designed and tested in the emergency department using nurse responders without a scoring system. METHODS: The vision, aphasia, and neglect (VAN) screening tool was designed to quickly assess functional neurovascular anatomy. While objective, there is no need to calculate or score with VAN. After training participating nurses to use it, VAN was used as an ELVO screen for all stroke patients on arrival to our emergency room before physician evaluation and CT scan. RESULTS: There were 62 consecutive code stroke activations during the pilot study. 19 (31%) of the patients were VAN positive and 24 (39%) had a National Institutes of Health Stroke Scale (NIHSS) score of ≥6. All 14 patients with ELVO were either VAN positive or assigned a NIHSS score ≥6. While both clinical severity thresholds had 100% sensitivity, VAN was more specific (90% vs 74% for NIHSS ≥6). Similarly, while VAN and NIHSS ≥6 had 100% negative predictive value, VAN had a 74% positive predictive value while NIHSS ≥6 had only a 58% positive predictive value. CONCLUSIONS: The VAN screening tool accurately identified ELVO patients and outperformed a NIHSS ≥6 severity threshold and may best allow clinical teams to expedite care and mobilize resources for ELVO patients. A larger study to both validate this screening tool and compare with others is warranted.

A preliminary investigation into the psychometric properties of the Dublin Extrapersonal Neglect Assessment (DENA): A novel screening tool for extrapersonal neglect.

Extrapersonal neglect is one clinical manifestation that can occur following stroke. Existing neglect assessment procedures have been criticised for lengthy administration and do not assess how extrapersonal space is affected. This study investigated the psychometric properties of a new, time-efficient screening tool for extrapersonal neglect. Full ethical approval was granted and consent obtained from 50 participants with first-time stroke. Participants were screened for extrapersonal neglect on two consecutive days by two raters using the Dublin Extrapersonal Neglect Assessment (DENA) to test inter-rater reliability. Construct validity of the DENA was investigated by comparing the DENA to the Catherine Bergego Scale (CBS). Additional analyses were calculated between the DENA and the extrapersonal items of the CBS (CBS-E). The kappa statistic, intraclass correlation coefficients (ICCs) and Bland Altman analyses were calculated to determine excellent inter-rater reliability (ICC 0.971, κ = .876) and significant correlation between the DENA and the CBS and CBS-E (ICC 0.870, 0.934, κ = .793, .833, respectively). Bland Altman analyses demonstrated acceptable levels of agreement between the DENA raters, and the DENA and CBS, with no systematic differences evident. The DENA provides clinicians with a quick and psychometrically sound screening tool for extrapersonal neglect to ensure this impairment is addressed in stroke rehabilitation.

Standardization of the face-hand test in a Brazilian multicultural population: prevalence of sensory extinction and implications for neurological diagnosis

OBJECTIVE: The face-hand test is a simple, practical, and rapid test to detect neurological syndromes. However, it has not previously been assessed in a Brazilian sample; therefore, the objective of the present study was to standardize the face-hand test for use in the multi-cultural population of Brazil and identify the sociodemographic factors affecting the results. METHODS: This was a cross sectional study of 150 individuals. The sociodemographic variables that were collected included age, gender, race, body mass index and years of education. Standardization of the face-hand test occurred in 2 rounds of 10 sensory stimuli, with the participant seated to support the trunk and their vision obstructed in a sound-controlled environment. The face-hand test was conducted by applying 2 rounds of 10 sensory stimuli that were applied to the face and hand simultaneously. The associations between the face-hand test and sociodemographic variables were analyzed using Mann-Whitney tests and Spearman correlations. Binomial models were adjusted for the number of face-hand test variations, and ROC curves evaluated sensitivity and specificity of sensory extinction. RESULTS: There was no significant relationship between the sociodemographic variables and the number of stimuli perceived for the face-hand test. There was a high relative frequency of detection, 8 out of 10 stimuli, in this population. Sensory extinction was 25.3%, which increased with increasing age (OR=1.4[1:01–1:07]; p=0.006) and decreased significantly with increasing education (OR=0.82[0.71-0.94]; p=0.005). CONCLUSION: In the Brazilian population, a normal face-hand test score ranges between 8–10 stimuli, and the results indicate that sensory extinction is associated with increased age and lower levels of education.

Estereopsia en niños pseudofáquicos / Stereopsis in pseudophakic children

La estereopsia es el grado máximo que nos brinda la binocularidad y se desarrolla en los niños entre los 3 y 6 meses. Objetivo: determinar la presencia de estereopsia en niños pseudofáquicos, así como los factores asociados a la presencia de estereopsia en estos pacientes. Métodos: se realizó un estudio descriptivo, longitudinal y retrospectivo donde se incluyeron 25 niños mayores de 8 años previamente operados de catarata pediátrica en el Instituto Cubano de Oftalmología Ramón Pando Ferrer, que acudieron a la consulta entre junio y noviembre del año 2015. Se determinaron las variables estereopsia, lateralidad, origen de la catarata, edad de diagnóstico, edad de la cirugía y agudeza visual mejor corregida. Resultados: la estereopsia fina (60" o menos) se detectó en el 28 por ciento de los pacientes, y en el 68 por ciento algún grado de esta. Fue más frecuente en los pacientes con pseudofaquia bilateral y con cataratas traumáticas o del desarrollo, pero sin mostrar diferencias significativas. Todos los pacientes con estereopsia presentaron una agudeza visual mejor corregida mayor de 0,5 en su ojo de peor visión, y estadísticamente este resultado fue significativo. Conclusiones: la cirugía de catarata pediátrica permite desarrollar estereopsia. La agudeza visual posoperatoria es un factor determinante de esta(AU)

Stereopsis is the highest degree of binocularity and occurs in children aged 3 to 6 months of life. Objective: to determine stereopsis in pseudophakic children as well as the factors involved in stereopsis in these patients. Method: a retrospective, longitudinal and descriptive study of 25 children older than 8 years, who had been previously operated on of pediatric cataract in the Ramon Pando Ferrer Cuban Institute of Opthalmology. They went to the hospital from June to November, 2015. The variables were stereopsis, laterality, origin of cataract, age at diagnosis, age at the time of surgery and best corrected visual acuity. Results: fine stereopsis (60" or less) was detected in 28 percent of the patients, and some degree of it in 68 percent of them. It was more frequent in patients with bilateral pseudophakia and with traumatic or developmental cataract, but differences were not significant. All the stereoscopic patients had best corrected visual acuity over 0.5 in its worst vision eye, being this result statistically significant. Conclusions: the pediatric cataract surgery allows developing stereopsis and the postoperative visual acuity is a determining factor(AU)

Cultural Adaptation of the Portuguese Version of the "Sniffin' Sticks" Smell Test: Reliability, Validity, and Normative Data.

The cross-cultural adaptation and validation of the Sniffin`Sticks test for the Portuguese population is described. Over 270 people participated in four experiments. In Experiment 1, 67 participants rated the familiarity of presented odors and seven descriptors of the original test were adapted to a Portuguese context. In Experiment 2, the Portuguese version of Sniffin`Sticks test was administered to 203 healthy participants. Older age, male gender and active smoking status were confirmed as confounding factors. The third experiment showed the validity of the Portuguese version of Sniffin`Sticks test in discriminating healthy controls from patients with olfactory dysfunction. In Experiment 4, the test-retest reliability for both the composite score (r71 = 0.86) and the identification test (r71 = 0.62) was established (p<0.001). Normative data for the Portuguese version of Sniffin`Sticks test is provided, showing good validity and reliability and effectively distinguishing patients from healthy controls with high sensitivity and specificity. The Portuguese version of Sniffin`Sticks test identification test is a clinically suitable screening tool in routine outpatient Portuguese settings.

Hallucinogen Persisting Perception Disorder and Risk of Suicide.

A 30-year-old male patient developed a hallucinogen persisting perception disorder (HPPD) after smoking cannabis laced with phencyclidine (PCP) or lysergic acid diethylamide (LSD) 10 years prior to hospital admission. Clinically, he reported seeing vivid, saturated colors and caricature-like objects. The patient described perceiving objects or people in motion as moving faster than normal. He reported living in a dream-like state and feeling numb and detached from other people and his surroundings. Upon pharmacotherapy initiation, facility transfer, and subsequent discharge from an acute psychiatry unit, he ultimately committed suicide. Although hallucinogen abuse is common in the United States, this case suggests that HPPD maybe significantly underdiagnosed and undertreated. In some cases, this oversight may perpetuate years of unnecessary patient suffering and can ultimately lead to severe depression and suicide.

The long-term outcome of extremely preterm (<28 weeks' gestational age) infants with and without severe retinopathy of prematurity.

BACKGROUND: Severe retinopathy of prematurity (ROP) is associated with an increased risk for ophthalmologic morbidity, but the long-term impact in other domains is less clear. The aim of the current study was to determine whether severe ROP was related to poorer visual, cognitive, and educational outcomes in a representative sample of EP adolescents, and whether this persisted after adjusting for confounding neonatal risk factors. METHOD: One hundred and eighty extremely preterm (EP; <28 weeks) adolescents (17-18 years) were assessed on a range of neurodevelopmental measures, including visual processing, IQ, visual learning, visual-motor integration, and academic achievement. EP adolescents were grouped according to ROP status, (1) severe ROP (stage 3 or greater) in the worse eye; or (2) no or mild ROP and were compared on each outcome. Longitudinal data were compared at 2, 5, 8, and 17-18 years for general cognitive outcome. RESULTS: The severe ROP group performed more poorly and had more impairments than the non-severe ROP group on measures of visual processing, visual-motor integration, visual learning, IQ, and some academic achievement tests at 17-18 years of age. Group differences diminished after controlling for perinatal risk factors (severe white matter injury, post-natal corticosteroid, and surgery in the neonatal period), and only visual acuity scores remained significantly different between the groups. IQ scores remained consistently lower in the severe ROP group over time, but the magnitude reduced after adjusting for perinatal risk factors. CONCLUSIONS: Extremely preterm children with severe ROP are at increased risk for ongoing visual processing difficulties and lower IQ compared with EP peers without severe ROP. While severe ROP is a predictor of long-term impairments, this association is largely mediated by other neonatal risk factors.

Dysthyroid Orbitopathy Presenting with Gaze-Evoked Amaurosis: Case Report and Review of the Literature.

BACKGROUND: Gaze-evoked amaurosis (GEA) describes visual loss associated with eccentric gaze that recovers when the eye is returned to primary position. Here we describe an unusual case of bilateral GEA as the presenting feature of dysthyroid orbitopathy. This is only the third such case to be reported in the literature and the first to feature bilateral GEA in all positions of gaze without accompanying proptosis or ophthalmoplegia. CASE PRESENTATION: A 50-year-old man who had recently commenced treatment for thyrotoxicosis presented with a 3-week history of typical GEA in both eyes in all positions of gaze. He subsequently developed a bilateral compressive optic neuropathy which was only partially responsive to high dose steroid therapy. CONCLUSION: Although an uncommon presenting feature of dysthyroid orbitopathy, GEA is an ominous symptom that may precede sight-threatening optic nerve compromise. When present, early immunosuppressive and/or decompressive treatment should be considered.

Photopsias: A Key to Diagnosis.

PURPOSE: To assess the character and cause of photopsias in vitreoretinal patients. DESIGN: Cross-sectional study. PARTICIPANTS: A total of 169 consecutive patients (217 eyes) with vitreoretinal disease presenting with a history of photopsias. METHODS: A total of 217 eyes with photopsias in 169 patients were evaluated. Photopsia assessment included (1) laterality (unilateral, bilateral but not simultaneous, bilateral, and simultaneous); (2) morphology (flash, zig-zag, strobe, scintillating scotoma, twinkling, other); (3) color (white, silver, yellow, combination, other); (4) location (temporal, central, other); (5) duration (quick, prolonged, constant, other); (6) frequency; (7) diurnal appearance (day, night, both); (8) stimuli (turning head or eyes, hypoglycemia, hyperglycemia, other); and (9) associated systemic or ocular signs and symptoms (headache, numbness, weakness, vertigo, syncope, diplopia, hypotension, floaters, other). MAIN OUTCOME MEASURES: Clinical photopsia features correlated with the causes of photopsias. RESULTS: Thirty-two photopsia causes were identified. The top 16 included posterior vitreous detachment (PVD) in 39.7% of eyes; retinal tear in 8.9% of eyes; neovascular age-related macular degeneration (AMD) in 7.9% of eyes; rhegmatogenous retinal detachment (RRD) in 7.5% of eyes; classic and ophthalmic migraine in 6.5% of eyes; hypoglycemia in 2.8% of eyes; vertebrobasilar insufficiency in 2.8% of eyes; non-AMD choroidal neovascularization in 2.3% of eyes; retinitis pigmentosa in 1.9% of eyes; severe cough in 1.9% of eyes; central serous chorioretinopathy in 1.4% of eyes; intraocular lens reflections in 0.9% of eyes; blue field entoptic phenomenon in 0.9% of eyes; Charles Bonnet syndrome in 0.9% of eyes; digitalis in 0.9% of eyes; and metastatic adenocarcinoma to the brain in 0.9% of eyes. The photopsias associated with PVD are typically quick (96%), with lightning/flash morphology (96%), white (87%), temporally located (86%), associated with new-onset floaters (85%), preferentially seen in dark (90%) rather than lighted environments (29%), and often initiated by head/eye movements (60%). Retinal detachment had a similar profile, but with more nontemporal photopsias (40%) (P = 0.01). The photopsias from neovascular AMD are more centrally located (83%), quick and repetitive (79%), seen in light (73%) and dark (63%) environments, have no inciting stimuli (84%), and are more likely to be nonwhite (40%). CONCLUSIONS: A pointed history for photopsias can reveal a cause that may not initially seem apparent. Thus, the history can play a key role in management decisions.

Biparietal variant of Alzheimer's disease: a rare presentation of a common disease.

Alzheimer's disease (AD) is a clinically heterogeneous disease that may have atypical presentations with focal cortical syndromes and relatively preserved episodic memory. The posterior variant of AD has two subtypes: occipitotemporal, presenting with visuoperceptive impairment, and biparietal, presenting with visuospatial dysfunction and apraxia. We report a case of a 51-year-old woman with progressive limb apraxia and choreiform movements. Her neuropsychological evaluation was compatible with dementia, and revealed ideomotor and ideational limb apraxia, severe visuoconstructive ability impairment, dyscalculia and posterior aphasia. Workup excluded metabolic, infectious, inflammatory or neoplastic causes, and hereditary conditions as Huntington's disease and familial AD. Cerebrospinal fluid biomarkers revealed ß-amyloid reduction and τ protein increase. Brain imaging showed marked biparietal atrophy and hypoperfusion, and widespread cortical ß-amyloid deposition. Biparietal variant of AD was diagnosed and acetylcholinesterase inhibitor treatment induced clinical stabilisation. AD may present with atypical features and a high clinical suspicion is necessary for an early diagnosis.

Olfactory function in elderly people and patients with Alzheimer's disease.

BACKGROUND: Olfactory function is an important sensory perception function that helps us detect the smell of spoiled food, dirty clothing, and gas leaks. If ageing and Alzheimer's disease (AD) are accompanied by a decline in olfactory function, this might reduce the ability to sense danger, placing the safety and hygiene of elderly people at risk. METHODS: Subjects in this study included 113 healthy subjects aged 20-89 years and 12 persons with AD aged 62-85 years. The healthy subjects were divided into three groups according to age: young-adult group (20-43 years), middle-adult group (45-69 years), and old-adult group (70-89 years). The Hasegawa Dementia Scale-Revised score of AD subjects ranged from 15 to 26. We developed and implemented an odour identification ability test and a situational judgement test using an odour stick to examine the impact of ageing and AD on olfactory function from the perspective of sensing danger. To examine the impact of mild AD on the olfactory function, we compared the scores between the AD group and the age-matched control group. RESULTS: The scores for the situational judgement and odour identification ability tests were significantly lower in an old-adult group than in the young-adult and middle-adult groups. A significant correlation was found between age and scores for both tests in the control group. The AD group exhibited significantly lower total scores on both tests compared with the age-matched controls. CONCLUSIONS: These results suggest that ageing and mild AD may reduce the ability to identify odours and judge situations based on odours.

The importance of visual field testing in idiopathic intracranial hypertension.

Idiopathic intracranial hypertension (IIH) is a disease of unknown cause typically affecting obese women in the childbearing years. Although headache is the most common symptom, the major morbidity of IIH is visual loss, with 5% to 10% of patients progressing to blindness. While about 95% of patients with IIH have visual loss documented by perimetry, only about one-third notice their visual loss because most loss occurs in the peripheral visual field. Since treatment decisions in IIH are made primarily by changes in visual field function, serial perimetry is the most critical test to obtain when following patients with IIH. This article describes the role of visual field testing in the monitoring of IIH patients in clinical practice, including its importance in communication among providers.

Visualizing Meyer's loop: A comparison of deterministic and probabilistic tractography.

BACKGROUND: Diffusion tensor tractography of the anterior extent of the optic radiation - Meyer's loop - prior to temporal lobe resection (TLR) may reduce the risk for postoperative visual field defect. Currently there is no standardized way to perform tractography. OBJECTIVE: To visualize Meyer's loop using deterministic (DTG) and probabilistic tractography (PTG) at different probability levels, with the primary aim to explore possible differences between methods, and the secondary aim to explore anatomical accuracy. METHODS: Twenty-three diffusion tensor imaging exams (11 controls and 7 TLR-patients, pre- and post-surgical) were analyzed using DTG and PTG thresholded at probability levels 0.2%, 0.5%, 1%, 5% and 10%. The distance from the tip of the temporal lobe to the anterior limit of Meyer's loop (TP-ML) was measured in 46 optic radiations. Differences in TP-ML between the methods were compared. Results of the control group were compared to dissection studies and to a histological atlas. RESULTS: For controls and patients together, there were statistically significant differences (p<0.01) for TP-ML between all methods thresholded at PTG ≤1% compared to all methods thresholded at PTG ≥5% and DTG. There were no statistically significant differences between PTG 0.2%, 0.5% and 1% or between PTG 5%, 10% and DTG. For the control group, PTG ≤1% showed a closer match to dissection studies and PTG 1% showed the best match to histological tracings of Meyer's loop. CONCLUSIONS: Choice of tractography method affected the visualized location of Meyer's loop significantly in a heterogeneous, clinically relevant study group. For the controls, PTG at probability levels ≤1% was a closer match to dissection studies. To determine the anterior extent of Meyer's loop, PTG is superior to DTG and the probability level of PTG matters.