A reticulo-frontal disconnection syndrome

Central hypoventilation and brainstem dysgenesis

We report on a newborn with congenital hypotonia, unilateral facial palsy, sucking and swallowing difficulties, velopalatine incoordination, and unilateral impairment of the auditory brainstem responses, attributable to brainstem dysgenesis. On follow-up, the child manifested developmental delay and central hypoventilation syndrome during sleep. The ventilation abnormality during sleep with insensitivity to hypercapnia, associated with unilateral facial paralysis, indicates a pontine lesion, including the parafacial respiratory group.

The Effects of Brain Damage on the Performance of Hand Movement Sequences

The frontal lobes, if damaged, may lead to a host of divergent abnormalities, depending on the extent, site, depth, and laterality of the damage. Because of the extensive connections which exist between the frontal lobes and the other systems of the brain, damage to a more remote system may cause frontal system disorder through disconnection. The Hand Movement Test (HMT, Kaufman & Kaufman, 1983) is thought to be sensitive to damage affecting these systems, although the test was developed for use with children rather than adults. This paper examines the effects of three diverse neuropsychological disorders, where damage to the frontal lobes or to their interconnections has been implicated, on hand movement sequencing performance in adults. The three groups studied included patients diagnosed with alcohol-related brain damage (n = 57), patients diagnosed with mild traumatic brain injury (n = 21), and patients diagnosed with age-related dementia (n = 30). HMT performance was significantly poorer in all three clinical groups relative to controls, supporting the addition of this brief, paediatric test in neuropsychological evaluations assessing these disorders.

Cognitive evolution in hypertensive patients: a six-year follow-up

BACKGROUND

Several studies have examined the links between hypertension, vascular damage, and cognitive impairment. The functions most commonly involved seem to be those associated with memory and executive function.

AIMS

1) to report the cognitive evolution in a cohort of hypertensive patients, 2) to identify the affected domains, and 3) to correlate the results obtained with blood pressure measurements.

MATERIALS AND METHODS

Observational 6-year follow-up cohort study including both males and females aged≥65 and ≤80 years, and hypertensive patients under treatment. Patients with a history of any of the following conditions were excluded: stroke, transient ischemic attack, diabetes mellitus, atrial fibrillation, cardiac surgery, dementia, or depression. Four neurocognitive evaluations were performed (at baseline and every 2 years). The tests used evaluated memory and executive function domain. Blood pressure was measured on every cognitive evaluation.

RESULTS

Sixty patients were followed for 76.4±2.8 months. The average age at baseline was 72.5±4.2 and 77.9±4.6 at 6 years (65% were women). Two patients were lost to follow up (3.3%) and 8 patients died (13.3%).The density incidence for dementia was 0.6% patients per year (pt/y) (n=3) and for depression was 1.6% pt/y (n=12). No changes were observed in either memory impairment or the Mini Mental State Examination (MMSE) results (p=ns) during follow-up. A progressive impairment of the executive function was shown regardless of the blood pressure measurements.

CONCLUSION

1) the incidence of dementia doubled to general population, 2) the initial memory impairment did not change during the evaluation period, 3) cognitive impairment worsened in the areas related to executive function (prefrontal cortex) regardless of the adequacy of anti-hypertensive treatment and blood pressure values.

Persistent symptoms in mild to moderate traumatic brain injury associated with executive dysfunction

In order to improve detection of subtle cognitive dysfunction and to shed light on the etiology of persistent symptoms after mild-to-moderate traumatic brain injury (TBI), we employed an experimental executive reaction time (RT) test, standardized neuropsychological tests, and diffusion tensor imaging (DTI). The Executive RT-Test, an Executive Composite Score from standardized neuropsychological tests, and DTI-indices in the midbrain differentiated between patients with persistent symptoms from those fully recovered after mild-to-moderate TBI. We suggest that persistent symptoms in mild-to-moderate TBI may reflect disrupted fronto-striatal network involved in executive functioning, and the Executive RT-Test provides an objective and novel method to detect it.

Metacognition in stroke: bedside assessment and relation to location, size, and stroke severity

BACKGROUND

Frontal syndromes are poorly represented on stroke scales, yet may constitute an important component of the neurologic deficit impacting treatment and rehabilitation efforts.

AIMS

To validate an assessment of a frontal network syndrome score (FNSS) in stroke and to ascertain the relationship of the FNSS to lesion location, volume, and severity in young people with stroke.

METHODS

Accrual through a cognitive stroke registry of young, alert, nonaphasic, nonencephalopathic, nonsubstance abuse prone people who were tested with the 16 domain FNSS within 4 weeks of their stroke. Lesion location was determined by the Cerefy 3-dimensional, digital, coxial brain atlas identifying 6 regions of cerebral interest. Lesion severity was assessed by the National Institute of Health Stroke Score and infarct volume was measured in cubic centimeters.

RESULTS

From a sample of 456 cases in the registry after exclusions of encephalopathy, depression, and aphasia, cases with frontal network syndrome encompassed 132 of 341 persons (39%). Of these patients (n=80) with mean age 45.7 years [confidence interval (CI): 43.4, 48.1], educational level 13.1 years (CI:12.5, 13.6), mean National Institute of Health Stroke Score of 3.3 (CI: 2.6, 4.0), and mean lesion volume 30.3 mL (CI: 13.7, 46.9), had full testing with the FNSS battery yielding sensitivity (93%), specificity (74%), positive predictive value (79%), negative predictive value (90%), and a good interrater reliability (kappa=0.89, P=0.001). Construct validity testing with 15 frontal neuropsychologic tests revealed good to excellent significant Pearson r values in 14 of 15 of the tests. There was no correlation (Pearson's) for lesion volume (r=0.07, P=0.52) but significant correlation with stroke severity (r=0.23, P=0.03). Analysis of variance testing of the FNSS revealed significant differences for all 6 domains without intergroup significant differences for frontal network syndrome domains in the stroke group.

CONCLUSIONS

The FNSS is a valid, practical measure of frontal syndromes in stroke. Frontal syndromes are common in young people with stroke and may be present no matter where the lesion, are not dependent on size of stroke and have a low correlation with stroke severity.

Cortical intercorrelations of frontal area volumes in schizophrenia

BACKGROUND

Abnormal regional volume intercorrelations between selected cortical areas in schizophrenia patients were previously reported in several MRI studies.

METHODS

A detailed analysis of frontal gray and white matter volume correlations with Brodmann's area volumes in the rest of the cortex was undertaken in normal subjects (n = 42) and patients with schizophrenia (n = 106), divided into good-outcome (n = 52) and poor-outcome (Kraepelinian; n = 54) subtypes.

RESULTS

Frontal gray matter volumes were correlated with temporal lobe volumes in schizophrenics but not in normal subjects. Some frontal-parietal and frontal-occipital correlations showed a similar pattern. In comparison to normal subjects, schizophrenia patients showed weaker or absent intercorrelations intrafrontally, specifically between left motor-premotor and eye-movement areas (4, 6, 8) and dorsolateral area 44, as well as between left areas 9 and 46 vs. area 24 (cingulate gyrus). Poor outcome among patients with schizophrenia was associated with weaker correlations between left frontal area 9 and both medial and lateral temporal cortices, as compared to normal subjects or good-outcome patients.

CONCLUSIONS

There appears to be a structural component in the task or symptom-related dysfunctional interactions between the frontal and more posterior cortical regions with preferential pathological involvement of frontotemporal and more limited involvement of frontoparietal and fronto-occipital systems in schizophrenia. Impaired regional associations within the frontal lobe, between left motor-premotor and Broca's areas, may play a role in language processing deficits in schizophrenia, while frontocingulate disconnection may result in working memory disturbances. Poor outcome may be associated with more widespread disconnections between prefrontal vs. cingulate and temporal regions in the left hemisphere, consistent with a disruption along the course of the left cingulum or uncinate bundles.

Cognitive impairment in isolated subtentorial stroke

BACKGROUND

Recent case reports have implicated subtentorial lesions of the brainstem or cerebellum as part of the neurocognitive circuitry.

AIM

To determine whether cognitive impairment is part of the neurological deficit in isolated brainstem (IBSS) or cerebellar stroke (ICS), using bedside screening and formal neurocognitive assessment of higher cortical function.

METHODS

Accrual occurred through a hospital based stroke registry. Cognitive bedside tests and neuropsychological tests were employed for the detection of higher cortical function. Scores from each test were converted to age and education based z-scores. Scores at or below -1.5 SD were clinically defined 'impaired'. Scores were averaged across tests in each functional area.

RESULTS

Of the stroke patients (n = 1360), the infarct was isolated within the brainstem (IBSS) in (45 of 120 or 38%) and isolated within the cerebellum (ICI) in (37 of 79 or 46.8%). Comparison of the IBSS patients with cognitive impairment in one or more domains to those with brainstem (24 of 45 or 53%) and hemispheric cerebral infarcts: (43 of 72 or 58%) (Pearson Chi Square) was not significantly different (P = 0.49). The admission Canadian Neurological Score (mean 10.2, 95% CI: 9.7-10.2) and Rankin score at 1 month (mean 1.7, 95% CI: 2.1-1.4). Comparison of the number of ICI patients with cognitive impairment in one or more domains (13 of 37 or 35.1%) to those with cerebellar and hemispheric cerebral infarcts who had abnormal cognitive testing in one or more domains (16 of 36 or 44.4%) (Pearson Chi Square) was not significantly different (P = 0.41). The mean admission Canadian Neurological Scores for the ICI cases was 10.9 (95% CI: 10.5-11.2) on average. Their mean admission Rankin score was 1.7 (95% CI: 1.4-2.1). Neuropsychological testing for frontal/executive skills, immediate and delayed memory, and visuospatial abilities (n = 15), revealed that frontal abilities were most impacted by the isolated strokes in these patients (average frontal impairment index = -1.29 +/- 0.79) followed by delayed recall of verbal and visual information (mean = -1.18 +/- 1.17). Immediate memory (-0.51 +/- 0.75) and visuoconstructive skills (-0.06 +/- 0.88) were relatively spared. Overall, 47% of the patients showed impairment on frontal tasks while 40% had significant impairment in delayed recall. In contrast, only 13% had scores below the cutoff for immediate memory and none fell below the cutoff for visuoconstructive skills.

CONCLUSION

Cognitive impairment is a common sequel of isolated subtentorial stroke. The frequency of impairment is similar either because of isolated brainstem or isolated cerebellar infarct, and similar to cognitive impairment with cerebral hemispheric lesions. Frontal networks or metacognition is the most frequently involved domain.

The diagnosis and neuropsychological assessment of adult attention deficit/hyperactivity disorder. Scientific study and practical guidelines

The recognition of attention deficit/hyperactivity disorder (ADHD) in adults is a well documented, but relatively new development. Investigations of the disorder have indicated that disturbances in behavior and adjustment are common. These disturbances may be linked to poorly developed executive functions. This paper reviews the neuropsychological studies that have compared persons with ADHD to normal controls and to psychiatric controls. The review indicates that persons with ADHD share many neuropsychological characteristics with other persons with serious psychiatric conditions, although those with ADHD may have a particular profile of slowed performance in tasks of sustained attention and set shifting, and their use of working memory may be particularly impaired. The implications of research for clinical assessment are discussed. We contend that a neuropsychological orientation is necessary for making the diagnosis and gaining a full understanding of adult ADHD. A model for clinical assessment is proposed which utilizes a neuropsychological orientation and the targeted administration of neuropsychological instruments. The careful use of neuropsychological measures is warranted in providing an elaborate picture of a person's functioning, although the use of neuropsychological tests is not necessary to make the diagnosis.

Autonomic activity during task performance in adults with closed head injury

Skin conductance (SC) and heart rate (HR) were recorded in two experiments in persons who had suffered a closed head injury (CHI) at least 2 years previously and in control subjects. Experiment 1 consisted of a rest period, a series of innocuous tones, and a short simple reaction time (RT) task. Experiment 2 consisted of initial and final rest periods and a longer RT task with constant and variable preparatory intervals. The results from both protocols showed no group differences in HR, SC levels, or SC fluctuations during rest periods, but the SC variables increased less to the task instructions in the CHI group. There were no differences in SC response frequency or magnitude to innocuous tones, but the CHI subjects had fewer SC responses to the RT stimuli in both experiments. SC responses to both innocuous tones and RT stimuli had longer latencies in the CHI group. The results show that selective deficits in tonic and phasic autonomic responding to meaningful, significant, or demanding situations and stimuli are long-term sequelae to CHI. These attenuated activation increases may be related to inadequate mobilization of processing resources and to behavioral deficits shown by these patients.

How can be best explain retrograde amnesia in human memory disorder?

I firstly consider general issues relating to our attempts to understand retrograde amnesia. Three main hypotheses are reviewed that have been proposed to account for retrograde amnesia. A theory is outlined to explain the dense autobiographical amnesia that is a focal phenomenon in some cases of severe head injury. This theory postulates that autobiographical retrieval requires the activation of a distributed network of cognitive operations, and that autobiographical amnesia results from the occurrence of multiple areas of pathology, distributed over both space and time.

Executive functioning following mild closed head injury

This study was aimed to identify impaired attentional components in mild CHI patients. The CHI features taken into account were age (< or = 30 vs. > 30 years), loss of consciousness (yes vs. no), and time after injury (few days vs. some months). The groups tested were composed of 26 patients and 26 controls (matched for age, sex and education). Experiment 1 used a dual-task paradigm (Umiltà et al., 1992), which taps executive functions. The double task-single task difference was greater for the CHI group, but only for patients older than 30 years and/or with consciousness loss. Two years after injury, some of these patients were retested: The results showed that this deficit was still present. Experiment 2 studied visual selective attention using the Navon (1977) paradigm. In this case, there were no differences between patients and controls. The results are discussed with reference to the anterior/posterior attention systems.

Attention and control deficits following closed head injury

This study was aimed at identifying the impaired attentional components in patients who had sustained a severe CHI several years before. A group of 14 CHI patients and a Control group (matched for age, sex and education) were tested. Experiment 1 used a dual-task paradigm (Umiltà et al., 1992). The double task-single task difference was greater for the CHI group, indicating a specific damage at a central executive stage where decision are made and responses are coordinated. Experiment 2 used a task-shifting paradigm (Morra and Roncato, 1986). The cost of shifting from one task to the other was greater for the CHI group, but only in the Short Series Condition where a new task-program could be pre-activated. Experiment 3 studied visual selective attention using Navon paradigm (1977); in this case, there was no difference between patients and controls.

Persistent neuropsychological deficits and vigilance impairment in sleep apnea syndrome after treatment with continuous positive airways pressure (CPAP)

The obstructive sleep apnea syndrome is characterized by nocturnal sleep disturbance, excessive daytime sleepiness and neuropsychological deficits in the areas of memory, attention, and executive tasks. In the present study, these clinical manifestations were assessed in apneic patients before and 6 months after treatment with nasally applied continuous positive airway pressure (CPAP). CPAP treatment was found to restore normal respiration during sleep and to normalize sleep organization. Daytime vigilance greatly improved with treatment but some degree of somnolence as compared to normal controls persisted. Similarly, most neuropsychological deficits normalized with treatment. The exception was for planning abilities and manual dexterity, two neuropsychological deficits that have been found to be highly correlated with the severity of nocturnal hypoxemia. These results raise the possibility that anoxic brain damage is a pathogenic factor in severe obstructive sleep apnea syndrome.