Biomedical subjects

J D Schmahmann

Publications and source records attributed to J D Schmahmann.

At least 19 recordsLinked to original sources

PubMed2000

Neuropsychological consequences of cerebellar tumour resection in children: cerebellar cognitive affective syndrome in a paediatric population.

Acquired cerebellar lesions in adults have been shown to produce impairments in higher function as exemplified by the cerebellar cognitive affective syndrome. It is not yet known whether similar findings occur in children with acquired cerebellar lesions, and whether developmental factors influence their presentation. In studies to date, survivors of childhood cerebellar tumours who demonstrate long-term deficits in cognitive functions have undergone surgery as well as cranial irradiation or methotrexate treatment. Investigation of the effects of the cerebellar lesion independent of the known deleterious effects of these agents is important for understanding the role of the cerebellum in cognitive and affective development and for informing treatment and rehabilitation strategies. If the cerebellar contribution to cognition and affect is significant, then damage in childhood may influence a wide range of psychological processes, both as an immediate consequence and as these processes fail to develop normally later on. In this study we evaluated neuropsychological data in 19 children who underwent resection of cerebellar tumours but who received neither cranial irradiation nor methotrexate chemotherapy. Impairments were noted in executive function, including planning and sequencing, and in visual-spatial function, expressive language, verbal memory and modulation of affect. These deficits were common and in some cases could be dissociated from motor deficits. Lesions of the vermis in particular were associated with dysregulation of affect. Behavioural deficits were more apparent in older than younger children. These results reveal that clinically relevant neuropsychological changes may occur following cerebellar tumour resection in children. Age at the time of surgery and the site of the cerebellar lesion influence the neurobehavioural outcome. The results of the present study indicate that the cerebellar cognitive affective syndrome is evident in children as well as in adults, and they provide further clinical evidence that the cerebellum is an essential node in the distributed neural circuitry subserving higher-order behaviours.

Adolescent↗

PubMed1999

Three-dimensional MRI atlas of the human cerebellum in proportional stereotaxic space.

We have prepared an atlas of the human cerebellum using high-resolution magnetic resonance-derived images warped into the proportional stereotaxic space of Talairach and Tournoux. Software that permits simultaneous visualization of the three cardinal planes facilitated the identification of the cerebellar fissures and lobules. A revised version of the Larsell nomenclature facilitated a simple description of the cerebellum. This atlas derived from a single individual was instrumental in addressing longstanding debates about the gross morphologic organization of the cerebellum. It may serve as the template for more precise identification of cerebellar topography in functional imaging studies in normals, for investigating clinical-pathologic correlations in patients, and for the development of future probabilistic maps of the human cerebellum.

Cerebellum↗

PubMed1998

The cerebellar cognitive affective syndrome.

Anatomical, physiological and functional neuroimaging studies suggest that the cerebellum participates in the organization of higher order function, but there are very few descriptions of clinically relevant cases that address this possibility. We performed neurological examinations, bedside mental state tests, neuropsychological studies and anatomical neuroimaging on 20 patients with diseases confined to the cerebellum, and evaluated the nature and severity of the changes in neurological and mental function. Behavioural changes were clinically prominent in patients with lesions involving the posterior lobe of the cerebellum and the vermis, and in some cases they were the most noticeable aspects of the presentation. These changes were characterized by: impairment of executive functions such as planning, set-shifting, verbal fluency, abstract reasoning and working memory; difficulties with spatial cognition including visual-spatial organization and memory; personality change with blunting of affect or disinhibited and inappropriate behaviour; and language deficits including agrammatism and dysprosodia. Lesions of the anterior lobe of the cerebellum produced only minor changes in executive and visual-spatial functions. We have called this newly defined clinical entity the 'cerebellar cognitive affective syndrome'. The constellation of deficits is suggestive of disruption of the cerebellar modulation of neural circuits that link prefrontal, posterior parietal, superior temporal and limbic cortices with the cerebellum.

Adult↗

PubMed1997

Anatomic organization of the basilar pontine projections from prefrontal cortices in rhesus monkey.

In our ongoing attempt to determine the anatomic substrates that could support a cerebellar contribution to cognitive processing, we investigated the prefrontal cortical projections to the basilar pons. A detailed understanding of these pathways is needed, because the prefrontal cortex is critical for a number of complex cognitive operations, and the corticopontine projection is the obligatory first step in the corticopontocerebellar circuit. Prefrontopontine connections were studied using the autoradiographic technique in rhesus monkey. The pontine projections were most prominent and occupied the greatest rostrocaudal extent of the pons when derived from the dorsolateral prefrontal convexity, including areas 8Ad, 9/46d, and 10. Lesser pontine projections were observed from the medial prefrontal convexity and area 45B in the inferior limb of the arcuate sulcus. In contrast, ventral prefrontal and orbitofrontal cortices did not demonstrate pontine projections. The prefrontopontine terminations were located preferentially in the paramedian nucleus and in the medial parts of the peripeduncular nucleus, but each cortical area appeared to have a unique complement of pontine nuclei with which it is connected. The existence of these corticopontine pathways from prefrontal areas concerned with multiple domains of higher-order processing is consistent with the hypothesis that the cerebellum is an essential node in the distributed corticosubcortical neural circuits subserving cognitive operations.

Animals↗

PubMed1997

Rediscovery of an early concept.

The study of the cerebellum has been dominated by interest in its role in movement and motor control. From the earliest days of the neuroscientific era, however, clinical reports and physiological and behavioral investigations have suggested that overt motor dysfunction is but one manifestation of cerebellar disease. The nature of cerebellar involvement in autonomic, sensory, and cognitive functions has been investigated for many years, and possible mechanisms that could subserve this relationship have been specifically addressed. This work has not been incorporated into the mainstream of neuroscience or clinical neurological thinking. This chapter traces the history of these early investigations that demonstrated the need to revise the notion that cerebellar function is confined to the motor realm. The collaboration across disciplines and the advances in the methods and concepts of contemporary neuroscience have facilitated the maturation of this field of inquiry. The "new" story of the cerebellum and cognition, in fact, represents the evolution of a century-old revolutionary concept.

Europe↗

PubMed1997

The cerebrocerebellar system.

If there is a cerebellar contribution to nonmotor function, particularly to cognitive abilities and affective states, then there must be corresponding anatomic substrates that support this. The cerebellum is strongly interconnected with the cerebral hemispheres in both feedforward (cerebral hemispheres to cerebellum) and feedback directions. This relationship has long been recognized, particularly with respect to the motor and sensory cortices. Investigations performed over the last decade however, have demonstrated for the first time the organization and strength of the connections that link the cerebellum with areas of the cerebral cortex known to be concerned with higher order behavior rather than with motor control. The feedforward projections from these higher order areas, namely the associative and paralimbic cortices, seem to be matched, at least in the limited but definite demonstrations to date, by cerebellar projections back to these same areas. These observations are important because they are congruent with the notion that cognitive functions are distributed among multiple cortical and subcortical nodes, each of which functions in concert but in a unique manner to produce an ultimate behavior pattern. This chapter describes the neural circuitry postulated to subserve the cerebellar contribution to nonmotor processing, particularly cognitive and affective modulation, and discusses the theoretical implications of these anatomic findings.

Affect↗

PubMed1997

Cerebellar cognitive affective syndrome.

There has been persistent uncertainty as to whether lesions of the cerebellum are associated with clinically significant disturbances of behavior and cognition. To address this question, 20 patients with diseases confined to the cerebellum were studied prospectively over a 7-year period and the nature and severity of the changes in neurological and mental function were evaluated. Neurological examination, bedside mental state testing, neuropsychological studies, and anatomic neuroimaging were administered at the time of presentation and during follow-up assessments. Behavioral changes were clinically prominent in patients with lesions involving the posterior lobe of the cerebellum and the vermis and, in some cases, overwhelmed other aspects of the presentation. These changes were characterized by an impairment of working memory, planning, set shifting, verbal fluency, abstract reasoning, and perseveration; visual-spatial disorganization, visual memory deficits, and logical sequencing; and a bland or frankly inappropriate affect. Lesions of the anterior lobe of the cerebellum produced only minor changes in executive and visual-spatial functions. This newly defined clinical entity is called the cerebellar cognitive affective syndrome. The constellation of deficits is suggestive of disruption of the cerebellar modulation of neural circuits than link frontal, parietal, temporal, and limbic cortices with the cerebellum.

Adult↗

PubMed1997

Therapeutic and research implications.

Investigations into the relationship between the cerebellum and nonmotor processing have produced a substantial body of evidence which seems to require a revision of accepted notions about the functional role of the cerebellum. This chapter presents a perspective on the contemporary and possible future therapeutic and research implications of these findings. These include the need for patients and their families to know of the behavioral consequences of cerebellar disease processes; potential approaches for improvement through rehabilitation therapies; and future treatment strategies, such as electrical stimulation of the cerebellum and psychosurgical approaches applied to the cerebellum. In addition, some areas of basic science investigation that could prove informative in understanding this relationship are addressed. It will be important to obtain a more complete characterization of the anatomy, physiology, and functional topography of the cerebellum in humans and in animal models, and a greater understanding of the clinical consequences of cerebellar lesions.

Animals↗

PubMed1997

Normal-pressure hydrocephalus with misleading features of irreversible dementias: a case report.

An 85-year-old man presented with the clinical triad (gait instability, dementia, and bladder and bowel incontinence), the ventriculomegaly, and the normal CSF pressure that characterize normal-pressure hydrocephalus (NPH). Diagnostic uncertainty was raised by an unusually rapid onset and a lack of initial response to CSF tap tests. Additionally, periodic sharp waves on EEG suggested the possibility of Creutzfeldt-Jakob disease, and positron emission tomography (PET) demonstrated a pattern of cerebral hypometabolism typical of Alzheimer's disease. Nevertheless, the diagnosis of NPH was supported by delayed improvement following CSF tap tests, and it was confirmed by a dramatic clinical recovery after CSF shunting, resolution of the EEG and PET abnormalities, and a normal brain biopsy. NPH remains one of the few reversible causes of dementia, and the presence of its core features, regardless of rate of onset or ancillary test results, warrants careful consideration of therapeutic intervention.

Activities of Daily Living↗

PubMed1995

Prefrontal cortex projections to the basilar pons in rhesus monkey: implications for the cerebellar contribution to higher function.

The feedforward limb of the cerebrocerebellar system is directed largely through the corticopontine pathway. We determined the extent to which higher order corticopontine projections are derived from prefrontal associative cortices by injecting anterograde tracers into multiple prefrontal regions in rhesus monkeys. Most prefrontopontine projections were derived from the dorsolateral and dorsomedial convexities, including areas 8A, 46 dorsal, 9, and 10; and lighter projections arose from medial and ventrolateral cortices. These findings strengthen the observation that the cerebrocerebellar system incorporates associative cerebral regions, and they enhance the notion that the cerebellum participates in the organization of cognitive function.

Animals↗

PubMed1995

Therapy for paraneoplastic neurologic syndromes in six patients with protein A column immunoadsorption.

BACKGROUND: Paraneoplastic neurologic syndromes, although rare, cause significant morbidity and mortality. They are thought to be immunologically mediated, but to date those involving the central nervous system (CNS) have not been particularly responsive to immunologic therapy. The use of the novel immunomodulator, protein A immunoadsorption, was explored to address this question. METHODS: Six patients with neurologic paraneoplastic syndromes were treated with this technique, using the "off line" method. Two hundred fifty ml of plasma was perfused through a column containing protein A covalently attached to a silica matrix. The plasma was then returned to the patient. RESULTS: Five of the patients responded to the therapy, with complete and durable responses in three patients with opsoclonus-myoclonus, objective, though transient, improvement in one patient with paraneoplastic brainstem encephalitis associated with a Merkel cell tumor, and stabilization and partial improvement in one patient with paraneoplastic limbic encephalitis. The patient without response developed a cutaneous vasculitis after the second treatment, and therapy was discontinued. CONCLUSIONS: This therapy appears beneficial for a number of paraneoplastic syndromes, most dramatically in the opsoclonus/myoclonus syndrome.

Adult↗

PubMed1993

Prelunate, occipitotemporal, and parahippocampal projections to the basis pontis in rhesus monkey.

We used tritiated amino acids to study projections to the basilar pons from prestriate cortices in 18 rhesus monkeys to determine how connectional and functional heterogeneity of these regions are reflected in corticopontine circuitry. Fibers travelled with those from other parasensory associative cortices before terminating in the pontine nuclei. Prelunate projections were derived from area 19 (OA) at the medial convexity (including areas V3 and PO) and from the lateral convexity dorsal to the caudal tip of the Sylvian fissure (including areas DP and the dorsal part of area V4d). Pontine projections also arose from area 19 (OA), and areas TF, TL, and TH in the posterior aspect of the parahippocampal gyrus. No pontine projections arose from the prelunate convexity ventral to the caudal tip of the Sylvian fissure (ventral part of area V4d and area V4v), area TEO, the inferior temporal gyrus, or the lateral ventral temporal region. Terminations in the pons were distributed in the dorsolateral and lateral nuclei, and the lateral part of the peripeduncular nucleus. Medial convexity injections produced more extensive rostrocaudal pontine labeling, as well as terminations in the extreme dorsolateral nucleus and the nucleus reticularis tegmenti pontis. Dorsal prelunate injections had additional terminations in the ventral pontine nucleus. Posterior parahippocampal gyrus injections resulted in discrete label in the lateral and dorsolateral nuclei. Corticopontine projections destined for the cerebellum appear to be derived from extrastriate areas concerned mainly with visual spatial parameters, visual motion, and the peripheral field of vision, but not from areas subserving visual object identification and the central field of vision. Pontine afferents from the posterior parahippocampal gyrus may facilitate a cerebellar contribution to visual spatial memory, particularly when invested with motivational valence.

Animals↗

PubMed1992

Course of the fiber pathways to pons from parasensory association areas in the rhesus monkey.

The course of the fiber pathways to pons from parasensory association areas in the rhesus monkey was investigated by injection of tritiated amino acids and the technique of autoradiography. Results confirm the projection to pons from parasensory association areas in the temporal, parietal, and occipital lobes and extend these observations to include the posterior parahippocampal gyrus. The findings reveal that the white matter of the posterior limb of the internal capsule above the midpoint of the lateral geniculate nucleus, and at the medial aspect of the lateral geniculate nucleus, comprise common regions through which these corticopontine fibers lead to the basis pontis. The fibers demonstrate a certain degree of topographic organization in the posterior limb of the capsule above the lateral geniculate nucleus and also in the cerebral peduncle. Taken together with previous observations concerning the termination patterns of these associative corticopontine projections, it would appear that the corticopontine system consists of segregated and partially overlapping pathways, which are to some extent distinguishable anatomically at each stage of their trajectory from origin to destination. Furthermore, the existence of a common area through which all parasensory associative input to pons is transmitted suggests that a precisely located lesion in this part of the corticopontocerebellar circuit may disrupt the cerebellar access to higher order information derived from the parasensory associative regions.

Animals↗

PubMed1992

Parietal pseudothalamic pain syndrome. Clinical features and anatomic correlates.

We studied six patients who developed spontaneous hemibody pain following lesions of the parietal lobe. The pain was characterized as burning or icelike, and was associated with impairment of pin and temperature appreciation. Computed tomographic scanning showed that the common area of involvement in all cases was the white matter deep to both the caudal insula and the opercular region of the posterior parietal cortex. We suggest that disruption of the interconnections between these cerebral cortical areas (including the second somatosensory representation, SII) and the thalamus, particularly the intralaminar and ventroposterior nuclei, may be responsible for producing a thalamocortical disconnection syndrome with spontaneous pain as its clinical manifestation.

Adult↗

PubMed1992

The mysterious relocation of the bundle of Türck.

The name bundle of Türck has become synonymous with the temporopontine tract. As details concerning this pathway have been confusing and incomplete we reviewed the papers of Ludwig Türck (1810-1868) to determine what in fact he originally described. Türck's pioneering degeneration studies provided great detail concerning the corticospinal tracts. Charcot recognized his contributions and used the eponym 'bundle of Türck' to denote the anterior corticospinal tract. Türck did not observe projections from the temporal lobe to the basis pontis, nor did he describe a temporopontine tract located at the most lateral aspect of the cerebral peduncle. The papers of Meynert, Flechsig and others reveal the origins of the current incorrect use of the eponym.

History, 17th Century↗

PubMed1991

Projections to the basis pontis from the superior temporal sulcus and superior temporal region in the rhesus monkey.

The present investigation was designed to determine the origins in the temporal lobe, and terminations in the pons, of the temporopontine pathway. Injections of tritiated amino acids were placed in multimodal regions in the upper bank of the superior temporal sulcus (STS), and in unimodal visual, somatosensory, and auditory areas in different sectors of the lower bank of the STS, the superior temporal gyrus (STG), and the supratemporal plane (STP). The distribution of terminal label in the nuclei of the basis pontis was studied using the autoradiographic technique. Following injections of isotope into the multimodal areas (TPO and PGa) in the upper bank of the STS, intense aggregations of label were observed in the extreme dorsolateral, dorsolateral, and lateral nuclei of the pons, and modest amounts of label were seen in the peripeduncular nucleus. The caudalmost area TPO projected in addition to the ventral and intrapeduncular pontine nuclei. The second auditory area, AII, and the adjacent auditory association areas of the STG and STP contributed modest projections to the dorsolateral, lateral, and peripedunuclar nuclei, but generally spared the extreme dorsolateral nucleus. The lower bank of the STS, which subserves central vision, the somatosensory associated region at the fundus of the rostral STS, and the primary auditory area did not project to the pons. The higher order, multimodal STS contribution to the corticopontocerebellar circuit may provide a partial anatomical substrate for the hypothesis that the cerebellum contributes to the modulation of nonmotor functions.

Amino Acids↗

PubMed1991

An emerging concept. The cerebellar contribution to higher function.

Recent clinical and research reports suggest that the cerebellum may contribute to the modulation of higher order behavior. This article presents a critical review of both earlier and more current clinical observations that raise this possibility, as well as a review of the salient laboratory data that appear to support this contention. It also summarizes the relevant anatomic work concerning the contributions to the corticopontocerebellar pathways from the higher order cerebral association areas, which have been implicated as partial anatomic substrates for this putative cerebellar role in higher function. Finally, it provides a framework for the understanding of this correlation, concludes with suggestions for future areas of investigation, and recommends that patients with cerebellar lesions be studied from a neurobehavioral point of view.

Aggression↗

PubMed1990

Anatomical investigation of projections from thalamus to posterior parietal cortex in the rhesus monkey: a WGA-HRP and fluorescent tracer study.

The parietothalamic projections have been shown to be heterogeneous and appear to be a reflection of the detailed architectonic parcellation of the parietal lobe. In the present study WGA-HRP injections were placed in the different subdivisions of the posterior parietal cortex of the rhesus monkey to determine whether a similarly complex pattern also exists in the thalamocortical pathway. Additionally, in an attempt to determine whether there is an intranuclear specificity of projections from individual thalamic nuclei to different subdivisions of the parietal lobe, multiple retrograde fluorescent tracers were injected into the rostral to caudal sectors of the parietal lobe of the same animal. Different subdivisions of the parietal lobe appear to receive different sets of thalamic input. Thus the superior parietal lobule (SPL) projections are derived from more lateral regions in the thalamus, arising predominantly from the lateral posterior (LP) and pulvinar oralis (PO) nuclei, with additional contributions from the pulvinar lateralis (PL) and pulvinar medialis (PM) nuclei. The inferior parietal lobule (IPL), by contrast, receives its projections from more medial thalamic regions, its main thalamic input originating from PM, and aided by LP, PL, and PO. Both the SPL and IPL also receive projections from the mediodorsal (MD), ventroposterior, ventrolateral, intralaminar, and limbic nuclei, albeit from different components within these nuclei. A topographical arrangement also exists in the thalamic projections to the rostral versus the caudal subdivisions of both the SPL and the IPL. Thus, in the SPL, the ventral posterolateral nucleus, pars oralis (VPLo), ventral lateral nucleus, pars oralis (VLo), and ventral lateral nucleus, pars medialis (VLm) project to rostral regions, whereas the PM and limbic nuclei, anteroventral (AV), and anteromedial (AM), project to area PGm on the medial convexity of the SPL. With respect to projections to the IPL, the ventral posteromedial (VPM) and PO nuclei project to rostral regions, whereas the limbic nuclei lateral dorsal (LD), AM and AV project only to the caudal most area, Opt. A rostrocaudal difference is reflected also within certain nuclei (LP, PO, and PM) that project to the SPL or IPL. Thus rostral parietal subdivisions receive projections from ventral regions within these thalamic nuclei, whereas caudal parietal afferents arise from the dorsal parts of these nuclei. Intervening cortical levels receive projections from intermediate positions within the nuclei. It therefore seems that the increasing architectonic and functional complexity as one moves from rostral to caudal in the SPL and IPL appear to be reflected in the thalamic afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗