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PubMed2001

Variability and asymmetry in the human precentral motor system. A cytoarchitectonic and myeloarchitectonic brain mapping study.

The morphology of the region of the primary motor cortex in the human brain is variable, and putative asymmetries between the hemispheres have been noted since the beginning of last century. Such variability may confound the results of clinical lesion or functional activation studies. We measured Brodmann area (BA) 4 and the identifiable precentral component of the pyramidal tract (PRPT) in 11 human post-mortem brains using techniques of quantitative cytoarchitectonic and myeloarchitectonic image analysis. Topography and variability in the localization of architectonic borders were analysed and mapped to a computerized spatial reference system, which consists of an individual in vivoMRI brain. All maps were superimposed to produce probabilistic maps of BA 4 and PRPT which can be co-registered with any image of brain structure or function that has also been transformed to Talairach coordinates. These maps can be readily applied to future brain mapping studies. We observed a considerable degree of variability between hemispheres (intra-individual) and between brains (inter-individual). The variation zones of BA 4 and PRPT differ from the templates of the Talairach atlas. Voxel-based morphometry shows significant side differences with larger volumes of PRPT in the left hemisphere than in the right hemisphere. This larger volume of the descending cortical motor fibres may be related to the known left-hemisphere dominance for handedness in >90% of the population. In contrast, BA 4 was symmetrically organized. The lack of a significant correlation between the size of BA 4 and the size of PRPT may relate to the fact that additional non-primary motor and sensory cortices contribute to the origins and size of the pyramidal tract proper.

Adult↗

PubMed2005

Spinal extradural schwannoma.

OBJECT: The authors endeavor to define the clinical and surgery-related profile of spinal nerve sheath tumors located in the extradural space outside both the dural sac and, apparently, the nerve roots' sleeve. METHODS: A series of 24 extradural schwannomas was retrospectively selected after reviewing the notes of spinal nerve sheath tumors surgically treated at La Sapienza University of Rome. Clinical data, tumor-related characteristics, and outcome were analyzed. Women predominantly harbored these tumors. On admission sensory nerve root dysfunction was infrequently reported, whereas pyramidal tract deficits were often present. The tumor, generally large, was most frequently located in the intermediate thoracic segments and high cervical region; only one was reported in the lumbosacral region. Considerable erosion of vertebral bodies was reported in almost one third of the cases. In four patients eloquent nerve roots, that of C-5 in three and that of S-1 in one, were involved with the tumor. Radical tumor resection, with preservation of the nerve roots, was possible in several cases, whereas in two patients manipulation and resection of the C-5 root produced transient and permanent, respectively, root palsy. At follow-up examination patients for whom walking was impossible before surgery were now able to walk. CONCLUSIONS: Extradural schwannomas can be distinguished from other nerve sheath tumors growing inside the spinal canal by their clinicoradiological features and unlikely nerve root origin. After surgery, recovery from pyramidal tract deficits, even severe, is noteworthy; in the authors' experience, however, resection of an involved appendicular root is more likely to result in a permanent and significant radicular deficit.

Adolescent↗

PubMed1999

Pyramidal control of heart rate and arterial pressure in cats.

The pyramidal control of the heart rate (HR) and the arterial pressure (AP) was investigated in the cat. Experiments were conducted in order to determine relative contribution of vagal and sympathetic components to this control. In eighteen anesthetized and curarized cats, electrical stimulations were applied to the pyramidal tract (PT), followed by pharmacological blockade of the sympathetic cardiac control or by bivagotomy. HR and mean arterial pressure (MAP) were recorded in response to pyramidal stimulations before and after bulbar transections sparing only the PT, beta 1-blockade by atenolol administration and/or bilateral vagotomy. Results showed that the stimulation of the PT elicits significant cardiac accelerations and MAP increases in all animals. Furthermore, bulbar transections allowed to conclude that pyramidal influences acted at bulbar level and not on spinal cardiovascular neurons. After beta 1-blockade by atenolol, HR increases were reduced by about 70% and those of MAP by about 30%; after bilateral vagotomy, cardioaccelerations were reduced by about 30% but no significant reductions of MAP were observed; finally, beta 1-blockade combined with vagal section suppressed cardioaccelerations and significantly reduced the MAP increases. These results suggest the existence of a direct cortical control, via the pyramidal tract, to cardiovascular centers of the medulla, probably mediated by pyramidal collaterals. This control appears to be organized following a reciprocal autonomic pattern where the suppression of the vagal inhibition is associated with a concomitant sympathetic excitation. The present work also provides data in favour of a central command coupling somatic programs and cardiac adjustments during motor acts.

Adrenergic beta-1 Receptor Antagonists↗

PubMed1983

Convergence of sensory inputs upon projection neurons of somatosensory cortex: vestibular, neck, head, and forelimb inputs.

Cortico-cortical neurons and pyramidal tract (PT) neurons of the cat cerebral cortex were tested for convergent inputs from electrically stimulated vestibular, neck, head and forelimb nerves. Neurons were recorded within forelimb and vestibular projection regions of cortical area 3a. Consideration was given to both suprathreshold and subthreshold inputs. Neither vestibular, neck nor head inputs were detected in the forelimb region of area 3a. In contrast, within the vestibular projection region of area 3a, 43% (6/14) of the cortico-cortical neurons and 63% (24/38) of the PT neurons received excitatory vestibular input. Inputs from the skin of the pinna (greater auricular nerve) were detected only for PT neurons (66%, 25/38). No inputs were detected from afferent nerves supplying the dorsal neck muscles biventer cervicis and complexus. Cortico-cortical and PT neurons receiving vestibular input also received convergent inputs originating from forelimb group I deep and low threshold cutaneous afferent fibers. Further, one half of the PT neurons with vestibular input (12/24) received input from three somatic sources: forelimb group I deep, forelimb low threshold cutaneous and greater auricular (head) nerves. The input connectivities suggest a role for these projection neurons of somatosensory cortex in the coordination of head and forelimb movements. The convergence of vestibular information with somatic input from the forelimb implies that vestibular-influenced neurons of area 3a projecting to the motor cortex or through the pyramidal tract would signal head position or movement with respect to proprioceptive feedback from the limbs.

Afferent Pathways↗

PubMed1986

Antidromic response to medullary pyramid stimulation in rats and its relation to that in cats.

The response evoked in the cerebral cortex of laboratory rats after stimulation of the medullary pyramid is surface-positive. It begins 0.9-1.6 ms after the stimulus, attains peak amplitude (up to 2 mV) in 0.8-1.2 ms and lasts 2-4 ms. It occurs throughout the anterior two-thirds of the dorsal cortex and is largest lateral to bregma, with a secondary maximum in the somatosensory area II. Although it depends on antidromic conduction in pyramidal tract fibers for its production, it varies in amplitude, configuration and latency at different recording sites and at the same sites on repeated trials. It reverses polarity deep in the cortex to become a large, negative wave deep in layer V, and maintains that polarity into the white matter. Current source density analysis reveals a strong sink in layer V, with a strong source just superficial to that sink and a weaker source in layer VI. The antidromic response disappears during spreading depression, but recovers more rapidly than the primary response evoked by skin stimulation. It decreases progressively in amplitude with continuous 200-Hz iterative stimulation, and recovers slowly at the end of stimulation. The primary response evoked by contralateral forepaw and hindpaw stimulation is highly localized, being entirely within the antidromic response distribution. The antidromic response in laboratory rats consists of a small, surface-positive component analogous to the pure antidromic response of cats, and of a large, surface-positive response analogous to that found in woodchucks, rabbits, opossums and slow lorises. It is argued that this latter response results from synaptic action in pyramidal tract axon collaterals, probably onto cells in layer V, rather than being a purely antidromic event.

Afferent Pathways↗

PubMed2005

Changes in corticospinal efficacy contribute to the locomotor plasticity observed after unilateral cutaneous denervation of the hindpaw in the cat.

We used microwire electrodes chronically implanted into the hindlimb representation of the motor cortex as well as into the pyramidal tract to test the hypothesis that the corticospinal system contributes to the locomotor plasticity that is observed after cutaneous denervation of the cat hindpaw. A total of 23 electrodes implanted into the motor cortex in three cats trained to walk on a treadmill produced phase-dependent, short-latency, twitch responses in hindlimb flexor and extensor muscles during locomotion. After a unilateral cutaneous denervation of the hindpaw, the cats showed transient deficits in locomotion, including a dragging of the hindpaw along the treadmill belt during the swing phase. This deficit rapidly recovered over the course of a few days. The recovery of locomotion was accompanied by an increase in the magnitude of the responses evoked in different muscles by the cortical stimulation at all 23 cortical sites. Response magnitude increased rapidly within the first 1-2 wk postdenervation before attaining a plateau at > or =3 wk. In two cats, for which detailed information was obtained, response magnitude in the knee flexor, semitendinosus (St), was increased by >250% at 14/18 sites (mean increase = 1,235%). Increased responses in the St to stimulation were also observed at two of the four pyramidal tract sites after the denervation but were relatively smaller (max = 593%) than those evoked by the cortical stimulation. We suggest that the denervation produces changes in both cortical and spinal excitability that, together, produce a change in corticospinal efficacy that contributes to the recovery of locomotor function.

Animals↗

PubMed1994

Quantification of D- and I-wave effects evoked by transcranial magnetic brain stimulation on the tibialis anterior motoneuron pool in man.

Transcranial stimulation in man evokes multiple descending volleys in the spinal cord giving rise to multiple subpeaks in a peri-stimulus-time histogram (PSTH) obtained from a cross-correlation of motor unit discharges with transcranial stimuli. The first volley is termed the D wave, as it is assumed to be evoked by direct excitation of pyramidal tract neurons, whereas the subsequent I waves appear to be generated by indirect excitation of the pyramidal tract neurons via cortical interneurons. It was the aim of this study to obtain an estimate of the effect induced by multiple volleys evoked by transcranial magnetic stimulation on the entire motoneuron pool of the tibialis anterior in awake subjects. A considerable part of a particular motoneuron pool was investigated by sampling responses of a large number (at least 19) from each muscle investigated. In total, three tibialis anterior muscles from three normal volunteers were studied. From each of the 63 units included in this study, a PSTH to 100 transcranial magnetic stimuli and a PSTH to 100 electrical stimuli given to the peroneal nerve were compiled. From the motor unit response to the peripheral nerve stimulation, the latency of the single-unit H reflex peak was obtained. This yielded, the timing of the subpeaks in response to the magnetic stimulation relative to the timing of the H reflex of the same unit, thus eliminating the influence of the peripheral conduction time from the motoneuron to the recording electrode. It was found that 50 (79%) of the motor units exhibited at least two subpeaks in response to the cortical stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2006

Diffusion-weighted MRI predicts prognosis in severe hypoglycemic encephalopathy.

A 20-year-old woman presented unconscious due to hypoglycemia after a self-administered insulin injection. Diffusion-weighted MRI (DWI), performed 5 days after admission, demonstrated heterogeneous high-intensity signal areas in both the cortex and subcortex but sparing the motor and sensory centers. On the 11th day after admission, she began making incomprehensible verbal sounds, eye opening spontaneously and moving her extremities with pyramidal tract signs. Three months later, she had aphasia, agnosia and apraxia but a normal gait without pyramidal tract signs or ataxia. DWI is thus considered useful to predict the functional outcome of patients with severe hypoglycemia.

Adult↗

PubMed1992

[Neuropathological study of amyotrophic lateral sclerosis in relation to aging].

It has been assumed that amyotrophic lateral sclerosis (ALS) involves precocious senility as one of its pathogenetic aspects. The authors studied 55 autopsied cases of ALS in relation to age at death, ranging from 42 to 86. The materials consisted of 8 cases in the fifth decade, 8 in the sixth, 20 in the seventh, 12 in the eighth, and 7 in the ninth. The total duration of illness ranged from 6 months to 14 years. The most distinct relationship was observed in the anterior horn lesion of the cervical enlargement which became less severe with advancing age, irrespective of the length of illness. Fifth decade cases showed marked atrophy with severe neuronal loss and fibrillary gliosis in the anterior horn, while those in the ninth decade showed slight changes which were similar to age-matched controls. On the other hand, pyramidal tract degeneration did not show any correlation to age at death or to length of illness. Pyramidal tract degeneration was found in all younger age group cases, being always severe. In the older age groups, however, the degeneration varied extremely in degree from case to case. Some cases showed severe degeneration comparable with that in the younger age groups, while the others had no findings suggesting degeneration. In addition, cases on artificial respirators had a longer duration of illness, and more marked degeneration in the anterior horn, irrespective of age. Our study did not reveal that senile changes including senile plaques and neurofibrillary tangles were more marked in ALS cases. No clinicopathological correlation with dementia was recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

[Multivariate analysis of spinal automatism in neurological diseases].

We investigated the relationship between spinal automatism (SA) and other neurological signs and symptoms (pyramidal, extrapyramidal, cerebellar, autonomic) by multivariate analysis in cervical spondylotic myelopathy (CSM) 112 cases, amyotrophic lateral sclerosis (ALS) 121 cases, and multiple system atrophy (MSA) 115 cases (olivo-ponto-cerebellar atrophy (OPCA) 55 cases, Shy-Drager syndrome (SDS) 42 cases, striato-nigral degeneration (SND) 18 cases). SA elicitation maneuver we used was pinprick stimulation at the dorsal pedal skin, and all cases showed twitched or phasic triple flexion pattern. As SA was elicited in 19 cases in CSM (17.0%), 23 cases (19.0%) in ALS, 36 cases (31.3%) in MSA, SA was more elicited in MSA than in ALS and CSM (p < 0.05, p < 0.01 by chi-squared test). In MSA, SA tended to be elicited more likely in SDS (21 cases, 50.0%) and in SND (8 cases, 44.4%) than in OPCA (7 cases, 12.7%) (p < 0.01 by chi-squared test). In MSA, the longer the duration of the disease became, the more SA was elicited, but not in ALS and CSM. Multivariate analysis (quantification method type II) showed that clinical signs as a statistical contribution factor for SA elicitation ranked Babinski's sign, micturition disturbance in ALS and CSM and Babinski's sign, orthostatic hypotension in MSA in order: In all 3 diseases, Babinski's sign and autonomic disturbance ranked higher. This conclusion suggested that SA was not always related to the pyramidal tract damage and was associated with the damage of small myelinated fibers in and/or around the pyramidal tract.

Adult↗

PubMed1977

Effect of thalamotomy and levodopa therapy on the speech of Parkinson patients.

The speech of three groups of Parkinson patients--nonsurgical, postunilateral and postbilateral thalamotomy--was evaluated. Dysarthria, bulbar motility and pyramidal tract indexes were determined for each patient. There was a statistically significant greater impairment in dysarthria and pyramidal tract indexes of patients with thalamotomy. L-Dopa and carbidopa therapy failed to significantly improve speech in any group.

Aged↗

PubMed1983

Adult spinal muscular atrophy. A report of four cases.

Four cases of spinal muscular atrophy (SMA) are reported, 3 with detailed autopsy findings. These are compared with 2 cases of typical amyotrophic lateral sclerosis (ALS) with neuropathological data. The 3 autopsy cases of SMA only showed decreased numbers of anterior horn cells in the spinal cord, with no change in the cortical pyramidal cells, including the Betz cells, and no degeneration of the pyramidal tracts, while the ALS cases showed loss both of lower and upper motor neurons and degeneration of the pyramidal tracts. In our opinion, the infantile, juvenile, adult, and late-life forms of SMA are really a single disease entity that occurs at varying ages and is separate from ALS. The term lower motor neuron disease would be preferable because the lesions are not limited to the spinal cord, but also occur in the brain stem.

Adult↗

PubMed1995

[A 65-year-old woman with dysarthria, dysphagia, weakness, and gait disturbance].

We report a 65-year-old woman with progressive dysarthria, dysphagia, weakness, and gait disturbance. The patient was well until 59 years of age (January of 1986) when she noted bilateral ptosis. One year later, she noted a gradual onset of difficulty in speech (articulation). Her speech slowly deteriorated and she noted weakness in chewing power and difficulty in swallowing in addition. In October 1987, she developed emotional incontinence. In January of 1988, she started to drag her left foot. She was admitted to our hospital on June 13 of 1988. On admission, she was alert and general physical examination was unremarkable. Neurologic examination revealed no dementia; her higher cerebral functions appeared intact. Ptosis was present bilaterally more on the right. She showed difficulty in opening her eyes on command; no contraction of the frontal muscles was seen upon attempted eye opening. There was a moderate limitation in the vertical gaze. Forced laughing and crying were seen. Facial muscles were moderately weak without apparent atrophy. The movement of the soft palate was very weak, and swallowing disturbance was more prominent for liquid staff. The tongue appeared somewhat small, however, no fasciculation was noted. Her step was small and the posture was stooped. Retropulsion was present, however, Romberg's sign was absent. No muscle atrophy was apparent, however, diffuse mile to moderate muscle weakness was noted in all four limbs. Cerebellar sign was absent. Deep tendon reflexes were exaggerated bilaterally, and Babinski sign was present on the left side. Sensation was intact. Routine blood tests were unremarkable as was a cranial CT scan. Her ptosis did not improve after 10 mg of edrophonium injection. CSF was also normal. She was transferred to another hospital but her neurological disabilities further progressed. In 1989, she was totally unable to move her limbs; she could only move her eyes; still consciousness was clear without dementia. She developed respiratory difficulty and expired on July 25, 1992. She was discussed in a neurological CPC, and the opinions were divided into ALS and primary lateral sclerosis (PLS). The chief discussant arrived at the conclusion that the patient might have had the pyramidal form of ALS. Postmorten examination revealed marked myelin pallor in the anterior as well as lateral corticospinal tracts. Pyramidal tract degeneration was prominent starting at the level of the cerebral peduncle and was continued to be seen until the level of lumbar cord. The number of anterior horn cells showed only slight decrease in the cervical level, however, it was normal in the lumbar cord.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗

PubMed1986

X linked hydrocephalus: a survey of a 20 year period in Victoria, Australia.

This study ascertained 164 males with non-communicating hydrocephalus in live or stillborn patients in Victoria. Australia in 1962 to 1982, after excluding those cases secondary to brain malformations other than aqueduct stenosis. Ascertainment was considered near complete, especially for the period since 1974, but details of the aqueduct pathology were inadequate in half the cases. A total of 91 families was seen to record detailed family information. The overall incidence of primary non-communicating hydrocephalus was estimated to be 0.6 +/- 0.2 per 1000 live and stillbirths, with three-fifths of the cases male. Twelve patients were classified as having definite X linked hydrocephalus and 13 others as probable cases of this condition. Deformities of the thumbs (generally adduction deformity) were present in nearly half of these cases. The pyramids were absent from sections of the medulla whenever these were available. Four of five survivors had signs suggesting pyramidal tract lesions, compared to four of 25 surviving non-X linked cases. The intellectual outcome was notably poorer in the X linked cases. Poor school performance was also described in five of 19 mothers of X linked cases but in only one of 64 mothers of the remaining cases. Familial recurrence in the whole group of patients was almost confined to the X linked families. The exceptions were two families in whom autosomal recessive inheritance is possible. It is important to remember X linked hydrocephalus in genetic counselling. Examination of the thumbs, search for clinical signs of pyramidal tract lesions, and anatomical examination of the pyramids in medullary sections are all important, along with careful questioning for a history of affected maternal relatives. The presence of any of these features is grounds for counseling on the basis of X linked inheritance. An empirical figure was derived to use when counseling about a male with non-communicating hydrocephalus in whom there is no adequate information about the thumbs or the pyramids: a 4% recurrence risk in male sibs and 2% in females.

Australia↗

PubMed1987

The coronal suture, a useful bony landmark in neurosurgery? Craniocerebral topography between bony landmarks on the skull and the brain.

In the present study the variation of the localisation and the course of the coronal suture (CS) was examined on the lateral skull X-ray. The study shows a variation of the localisation and course of the CS from the average position within +/- 4 mm in 65-77% and extreme differences between minimum and maximum values between 16 and 21 mm. The CS has also a considerable variation in its localisation relative to the precentral gyrus. Additionally the craniocerebral relationships and the localisation of the precentral gyrus and pyramidal tract are altered by the lesion or the space occupying process itself. A more exact localisation of the precentral gyrus, respectively the pyramidal tract can be obtained with CT and intraoperative cortical stimulation of the motor strip.

Brain↗

PubMed1990

Reversible neural inactivation by cooling in anesthetized and freely behaving rats.

The design and use of a miniaturized cryoprobe to allow reversible neural inactivation were investigated in the rat. Tissue temperature measurements around the cryoprobe in the cerebellum of anesthetized rats established that significant heat loss (lower than 20 degrees C) was localized within 1.5 mm of the cryoprobe tip. To physiologically test the effectiveness of the cryoprobe, two specific behaviors mediated by well defined neural structures were measured; electrically elicited hindleg flexion in ketamine-anesthetized rats, mediated by the pyramidal tract; and the acoustic startle reflex in freely behaving rats, mediated by the ventral nucleus of the lateral lemniscus. Cooling of the pyramidal tract at a tip temperature of -5 degrees C reversibly blocked electrically elicited hindleg flexions within about 21 s. Cooling of the ventral nucleus of the lateral lemniscus at 0 degrees C reversibly blocked the acoustic startle reflex. These effects were obtained when the cryoprobe tip was within 0.5 mm of the respective neural targets. The results suggest that cooling produces fully reversible neural blockade with a very rapid onset and offset. The advantages and limitations of cooling in the rat are discussed.

Anesthesia↗

PubMed1970

Recovery of neuronal function after prolonged cerebral ischemia.

Cats were submitted to complete cerebral ischemia by clamping the innominate and subclavian arteries and simultaneously lowering the systemic blood pressure. Neuronal function was assessed by recording the electroencephalogram and the anti- and orthodromic activation of the pyramidal tract. A full recovery of the pyramidal response and even of evoked electroencephalographic activity occurred after ischemia of more than 1 hour's duration.

Animals↗

PubMed1998

Nervous system defects of AnkyrinB (-/-) mice suggest functional overlap between the cell adhesion molecule L1 and 440-kD AnkyrinB in premyelinated axons.

The L1 CAM family of cell adhesion molecules and the ankyrin family of spectrin-binding proteins are candidates to collaborate in transcellular complexes used in diverse contexts in nervous systems of vertebrates and invertebrates. This report presents evidence for functional coupling between L1 and 440-kD ankyrinB in premyelinated axons in the mouse nervous system. L1 and 440-kD ankyrinB are colocalized in premyelinated axon tracts in the developing nervous system and are both down-regulated after myelination. AnkyrinB (-/-) mice exhibit a phenotype similar to, but more severe, than L1 (-/-) mice and share features of human patients with L1 mutations. AnkyrinB (-/-) mice exhibit hypoplasia of the corpus callosum and pyramidal tracts, dilated ventricles, and extensive degeneration of the optic nerve, and they die by postnatal day 21. AnkyrinB (-/-) mice have reduced L1 in premyelinated axons of long fiber tracts, including the corpus callosum, fimbria, and internal capsule in the brain, and pyramidal tracts and lateral columns of the spinal cord. L1 was evident in the optic nerve at postnatal day 1 but disappeared by postnatal day 7 in mutant mice while NCAM was unchanged. Optic nerve axons of ankyrinB (-/-) mice become dilated with diameters up to eightfold greater than normal, and they degenerated by day 20. These findings provide the first evidence for a role of ankyrinB in the nervous system and support an interaction between 440-kD ankyrinB and L1 that is essential for maintenance of premyelinated axons in vivo.

Animals↗