Somatic motor efferents in multiple system atrophy with autonomic failure: a clinico-pathological study

Neurophysiological differentiation of upper motor neuron damage in neurodegenerative disorders

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ALS and MSA presented with similar profiles of upper motor neuron signs.

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Central motor conduction time was more abnormal in ALS than in MSA.

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Different structures may be involved in ALS and MSA along the corticospinal tract.

Objective

Using transcranial magnetic stimulation (TMS) to delineate upper motor neuron (UMN) signs of two neurodegenerative disorders: amyotrophic lateral sclerosis (ALS) and multiple system atrophy (MSA).

Methods

Medical records including clinical signs for UMN damage and TMS results were reviewed retrospectively. The UMN signs were classified into none, mild, and severe based on neurological examination of various reflexes. Then TMS-elicited motor evoked potentials (MEPs) were recorded from a hand and a leg muscle to calculate the central motor conduction time (CMCT), which represents fast, mono-synaptic conduction along the corticospinal tract. Relations between the UMN signs and CMCT were analysed for the two diseases.

Results

Prevalence and severity of the UMN signs for ALS and MSA were comparable for both upper and lower limbs. However, abnormality in CMCT was found more frequently in ALS: CMCT abnormalities were found in upper limbs for 44% in ALS patients but only for 7% in MSA patients; CMCT abnormalities in lower limbs were 55% in ALS and 20% in MSA. Some ALS patients showed abnormal CMCT in limbs without UMN signs, which was not true for most MSA patients.

Conclusions

The abnormalities of CMCT were different in ALS and MSA, even for those who clinically had similar UMN signs. Sometimes, CMCT can reveal UMN damage in the absence of clinical UMN signs. Differences presumably derive from selective degeneration of different fibres in the motor descending pathways. Longitudinal studies must be conducted to accumulate neuroimaging and pathological findings.

Significance

CMCT can be useful to differentiate ALS and MSA.

Effects of differences in age and body height on normal values of central motor conduction time determined by F-waves

OBJECTIVES

To investigate the effect on central motor conduction time (CMCT) based on the relationship between age and height in normal subjects.

DESIGN

Retrospective study.

METHODS

One hundred and ninety nine normal subjects (107 men and 92 women; mean age 39.0 ± 16.4 years; mean height 164.5 ± 8.8 cm) participated in the study. The approximate ages of subjects were as follows: 82 (20-29 years old), 32 (30-39 years old), 32 (40-49 years old), 28 (50-59 years old), and 25 (≧60 years old). The heights of 9, 49, 79, 53, and 9 subjects were <150 cm, 150-160 cm, 160-170 cm, 170-180 cm, and >180 cm, respectively. CMCT- abductor digiti minimi (ADM) and abductor hallucis (AH) were calculated by subtracting the peripheral motor conduction time (PMCT) from the onset latency of motor evoked potentials (MEPs) evoked by transcranial magnetic stimulation. PMCT was calculated from the latencies of the compound muscle action potentials (CMAPs) and F-waves as follows: (latency of CMAPs + latency of F-waves -1)/2.

OUTCOME MEASURES

CMCT-ADM and CMCT-AH.

RESULTS

The normative values were 5.2 ± 0.8 ms and 11.8 ± 1.3 ms for CMCT-ADM and CMCT-AH, respectively. CMCT-ADM was not significantly correlated with age (P = 0.196) and body height (P = 0.158). CMCT-AH had significantly positive, linear correlations with age and body height (CMCT-AH = 0.014 × age + 10.971, P = 0.011, R = 0.179 and CMCT-AH = 0.026 × body height + 7.158, P = 0.010, R = 0.182).

CONCLUSIONS

We suggest normative values of 3.2-7.2 ms in CMCT-ADM for subjects exerting slight effort on ADM regardless age and body height. CMCT-AH had significantly positive, linear correlations with age and body height.

Involvement of Peripheral Nerves in the Transgenic PLP-α-Syn Model of Multiple System Atrophy: Extending the Phenotype

Multiple system atrophy (MSA) is a fatal, rapidly progressive neurodegenerative disease with (oligodendro-)glial cytoplasmic α-synuclein (α-syn) inclusions (GCIs). Peripheral neuropathies have been reported in up to 40% of MSA patients, the cause remaining unclear. In a transgenic MSA mouse model featuring GCI-like inclusion pathology based on PLP-promoter driven overexpression of human α-syn in oligodendroglia motor and non-motor deficits are associated with MSA-like neurodegeneration. Since α-syn is also expressed in Schwann cells we aimed to investigate whether peripheral nerves are anatomically and functionally affected in the PLP-α-syn MSA mouse model.

Multiple system atrophy: alpha-synuclein and neuronal degeneration

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder that encompasses olivopontocerebellar atrophy (OPCA), striatonigral degeneration (SND) and Shy-Drager syndrome (SDS). The histopathological hallmark is the formation of alpha-synuclein-positive glial cytoplasmic inclusions (GCIs) in oligodendroglia. alpha-synuclein aggregation is also found in glial nuclear inclusions, neuronal cytoplasmic inclusions (NCIs), neuronal nuclear inclusions (NNIs) and dystrophic neurites. We evaluated the pathological features of 102 MSA cases, and presented the pathological spectrum of MSA and initial features of alpha-synuclein accumulation. We found that 39% of the 102 cases showed equivalent SND and OPCA pathologies, 33% showed OPCA- and 22% showed SND-predominant pathology, whereas 6% showed extremely mild changes. Our pathological analysis indicated that OPCA-type was relatively more frequent and SND-type was less frequent in Japanese MSA cases, compared to the relatively high frequency of SND-type in Western countries, suggesting that different phenotypic patterns of MSA may exist between races. In the early stage, in addition to GCIs, NNIs and diffuse homogenous alpha-synuclein staining in neuronal nuclei and cytoplasm were observed in lesions in the pontine nuclei, putamen, substantia nigra, locus ceruleus, inferior olivary nucleus, intermediolateral column of thoracic spinal cord, lower motor neurons and cortical pyramidal neurons. A subgroup of MSA cases with severe temporal atrophy showed numerous NCIs, particularly in the limbic system. These findings suggest that primary non-fibrillar and fibrillar alpha-synuclein aggregation also occur in neurons. The oligo-myelin-axon-neuron complex mechanism, along with the direct involvement of neurons themselves, may synergistically accelerate the degenerative process of MSA.

Pyramidal tract degeneration in multiple system atrophy: the relevance of magnetization transfer imaging

The clinical features of multiple system atrophy (MSA) include four domains: autonomic failure/urinary dysfunction, Parkinsonism, cerebellar ataxia, and corticospinal tract dysfunction. Although the diagnosis of definite MSA requires pathological confirmation, magnetic resonance imaging (MRI) studies have been shown to contribute to the diagnosis of MSA. Although pyramidal tract dysfunction is frequent in MSA patients, signs of pyramidal tract involvement are controversially demonstrated by MRI. We evaluated the pyramidal involvement in 10 patients (7 women) with clinically probable MSA, detecting the presence of spasticity, hyperreflexia, and Babinski sign, as well as demonstrating degeneration of the pyramidal tract and primary motor cortex by MRI in all of them. Our article also discusses key radiological features of this syndrome. In MSA, pyramidal tract involvement seems to be more frequent than previously thought, and the clinicoradiological correlation between pyramidal tract dysfunction and degeneration may contribute to the understanding of the clinical hallmarks of MSA. MRI may also add information regarding the differential diagnosis of this syndrome.

Motor neuron involvement in experimental lumbar nerve root compression: a light and electron microscopic study

STUDY DESIGN

The aim of this study is to investigate changes in lumbar motor neurons induced by mechanical nerve root compression using an in vivo model. This study is to investigate the changes of lumbar motor neuron induced by mechanical nerve root compression using in vivo model.

OBJECTIVES

The effect of axonal flow disturbance induced by nerve root compression was determined in lumbar motor neuron.

SUMMARY OF BACKGROUND DATA

The lumbar motor neuron should not be overlooked when considering the mechanism of weakness, so it is important to understand the morphologic and functional changes that occur in motor neurons of the spinal cord as a result of nerve root compression. However, few studies have looked at changes of neurons within the caused by disturbance of axonal flow, the axon reaction, chromatolysis, and cell death as a result of mechanical compression of the ventral root.

METHODS

In mongrel dogs, the seventh lumbar nerve root was compressed for 1 week, or 3 weeks using a clip. Morphologic changes of the motor neurons secondary to the axon reaction were examined by light and electron microscopy.

RESULTS

Light and electron microscopy showed central chromatolysis of motor neurons in the lumbar cord from 1 week after the start of compression. After 3 weeks, some neurons undergoing apoptosis were seen in the ventral horn.

CONCLUSION

It is important to be aware that, in patients with nerve root compression due to lumbar disc herniation or lumbar canal stenosis, dysfunction is not confined to degeneration at the site of compression but also extends to the motor neurons within the lumbar cord as a result of the axon reaction. Patients with weakness of lower leg should therefore be fully informed of the fact that these symptoms will not resolve immediately after surgery.

Pupil abnormalities in selected autonomic neuropathies

Examination of the pupil provides an opportunity to detect disturbances in the autonomic innervation of the eye. The pupil is frequently affected in patients with generalized autonomic neuropathies. This literature review confirms a high prevalence of sympathetic deficits and parasympathetic deficits in acute or subacute dysautonomia, diabetes, amyloidosis, pure autonomic failure, paraneoplastic syndromes, Sjögren syndrome, familial dysautonomia, and dopamine beta-hydroxylase deficiency. It confirms the relative scarcity of a pupil abnormality in patients with multiple system atrophy. There are difficulties in clinical diagnosis of pupil abnormalities and interpretation of pupil pharmacologic tests, particularly when combined sympathetic and parasympathetic deficits are present.

Involvement of precerebellar nuclei in multiple system atrophy

In this semiquantitative study based on 26 post-mortem cases, we describe the involvement of precerebellar nuclei in multiple system atrophy (MSA), a progressive degenerative disorder of the human central nervous system characterized by abnormal, argyrophilic and alpha-synuclein immunopositive intracellular inclusions within selectively vulnerable oligodendrocytes and nerve cells. The Campbell-Switzer silver-pyridine technique with alpha-synuclein immunoreactions using 100-microm thick sections is recommended over more conventional methods, thereby permitting visualization of the pertinent lesions in greater detail and facilitating post-mortem diagnosis of MSA specimens. Affected oligodendrocytes occur in specific fibre tracts and grey matters, with most pathology being observed in projections from the precerebellar nuclei to the cerebellum (ponto-cerebellar, olivo-cerebellar, reticulo-cerebellar tracts) and in descending/ascending fibre tracts of the motor system (cortico-pontine, cortico-bulbar, cortico-spinal, spino-reticular, spino-olivary, spino-cerebellar tracts). Three types of abnormal intraneuronal aggregations occur: (i) a loosely woven network within the cell nucleus; (ii) a latticework accumulating in peripheral portions of the cell body; and (iii) irregularly outlined patches of compact, intensely argyrophilic material usually located within deposits of lipofuscin granules. Counter-staining for the presence of extraneuronal lipofuscin can aid neuropathologists in the recognition of lost existent neurones in MSA. Neurones with inclusion bodies occur in the inferior olivary nuclear complex, lateral reticular nucleus, external cuneate nucleus, conterminal nucleus, interfascicular nucleus, nucleus of Roller, dorsal paramedian reticular nucleus, subventricular nucleus, arcuate nucleus, pontobulbar body and pontine grey. The lateral reticular nucleus and accessory nuclei of the inferior olive sustain the most damage and reveal prominent neuronal loss, followed by the pontobulbar body and arcuate nucleus. The uniformly bilateral damage and, in some cases, even obliteration of the nuclei studied, supply additional evidence for the pathoanatomical substrata of the cerebellar dysfunction that reportedly emerges in the clinical course of MSA.

Progression and prognosis in multiple system atrophy: an analysis of 230 Japanese patients

We investigated the disease progression and survival in 230 Japanese patients with multiple system atrophy (MSA; 131 men, 99 women; 208 probable MSA, 22 definite; mean age at onset, 55.4 years). Cerebellar dysfunction (multiple system atrophy-cerebellar; MSA-C) predominated in 155 patients, and parkinsonism (multiple system atrophy-parkinsonian; MSA-P) in 75. The median time from initial symptom to combined motor and autonomic dysfunction was 2 years (range 1-10). Median intervals from onset to aid-requiring walking, confinement to a wheelchair, a bedridden state and death were 3, 5, 8 and 9 years, respectively. Patients manifesting combined motor and autonomic involvement within 3 years of onset had a significantly increased risk of not only developing advanced disease stage but also shorter survival (P < 0.01). MSA-P patients had more rapid functional deterioration than MSA-C patients (aid-requiring walking, P = 0.03; confinement to a wheelchair, P < 0.01; bedridden state, P < 0.01), but showed similar survival. Onset in older individuals showed increased risk of confinement to a wheelchair (P < 0.05), bedridden state (P = 0.03) and death (P < 0.01). Patients initially complaining of motor symptoms had accelerated risk of aid-requiring walking (P < 0.01) and confinement to a wheelchair (P < 0.01) compared with those initially complaining of autonomic symptoms, while the time until confinement to a bedridden state and survival were no worse. Gender was not associated with differences in worsening of function or survival. On MRI, a hyperintense rim at the lateral edge of the dorsolateral putamen was seen in 34.5% of cases, and a 'hot cross bun' sign in the pontine basis (PB) in 63.3%. These putaminal and pontine abnormalities became more prominent as MSA-P and MSA-C features advanced. The atrophy of the cerebellar vermis and PB showed a significant correlation particularly with the interval following the appearance of cerebellar symptoms in MSA-C (r = 0.71, P < 0.01, r = 0.76 and P < 0.01, respectively), but the relationship between atrophy and functional status was highly variable among the individuals, suggesting that other factors influenced the functional deterioration. Atrophy of the corpus callosum was seen in a subpopulation of MSA, suggesting hemispheric involvement in a subgroup of MSA patients. The present study suggested that many factors are involved in the progression of MSA but, most importantly, the interval from initial symptom to combined motor and autonomic dysfunction can predict functional deterioration and survival in MSA.

Aberrant pyramidal tract in the medial lemniscus of the human brainstem: normal distribution and pathological changes

We examined the consistency of the so-called aberrant pyramidal tract (APT) in 150 consecutive autopsied human brains using the modified Bielschowsky stain for axons. We were able to identify the APT in all brains except for one with holoprosencephaly. The APT left the pyramidal tract within the crus cerebri and passed in the medial lemniscus of the pons through the upper medulla oblongata. In 13 of the 63 brains with cerebrovascular diseases, wallerian degeneration was found in the APT on the ipsilateral side of the cerebral lesions. Further, the APT showed depletion of small-sized fibers in 2 of the 5 brains with multiple-system atrophy. These findings confirmed that the APT is a normal descending fiber tract and a part of the pyramidal tract.

Nerve conduction studies in multiple system atrophy

To study the frequency and severity of peripheral neuropathy in multiple system atrophy (MSA), we performed nerve conduction studies in 42 MSA patients suffering from either cerebellar MSA (MSA-C) or parkinsonian MSA (MSA-P). Abnormal nerve conduction was present in 24% of the patients. Abnormalities were significantly more frequent in MSA-P (43%) compared to MSA-C (14%). Motor nerve conduction velocities were reduced in 4% of the MSA-C and in 7% of the MSA-P patients. Abnormal compound muscle action potentials were more frequent in MSA-P (29% versus 7% in MSA-C) pointing to a more pronounced loss of motor axons in this subgroup. Sensory nerve conduction velocities were abnormal in 4% of the MSA-C and 14% of the MSA-P patients, and mean sensory nerve action potentials were normal in all MSA-C and reduced in 7% of the MSA-P patients. The data provide evidence that the peripheral nervous system is differentially affected in MSA-C and MSA-P.

Upper motor neuron lesions in stroke patients do not induce anterograde transneuronal degeneration in spinal anterior horn cells

BACKGROUND AND PURPOSE

To determine whether upper motor neuron lesions in stroke can cause transneuronal degeneration of lower motor neurons, we assessed spinal anterior horn cells in patients dying with poststroke hemiplegia.

METHODS

Subjects were four stroke patients with severe left hemiplegia and four age-matched control subjects who died of nonneurological disease. After histological processing and staining, cytoarchitectonic assessment was made of all neurons in the ventral horns of the 4th lumbar segment of the spinal cord according to cell diameter and topography.

RESULTS

In the four stroke patients, no differences were seen in anterior horn cell populations or diameter and size distribution patterns between affected and unaffected sides or between these patients and the control subjects.

CONCLUSIONS

The present quantitative analysis provides no evidence of anterograde transneuronal degeneration of lower motor neurons after upper motor neuron damage in stroke patients.

Sensory and motor evoked potentials in multiple system atrophy: a comparative study with Parkinson's disease

Somatosensory evoked potentials (SEPs) to median nerve stimulation and motor evoked potentials to transcranial magnetic stimulation (TMS) of the motor cortex were studied in 15 patients with multiple system atrophy (MSA) and compared with matched groups of 20 patients with idiopathic Parkinson's disease (PD) and of 20 normal controls (NCs). No SEP latency or amplitude abnormalities were observed, and, in particular, the frontal N30 component was not significantly depressed. No differences in TMS threshold for evoking responses in relaxed or active thenar muscles were observed. The mean central motor conduction time was normal for the biceps brachii and opponens pollicis muscles and prolonged in the MSA group for the tibialis anterior muscle. Recording SEPs is not useful to differentiate MSA from PD, while the presence of central motor conduction abnormalities may bring into question the diagnosis of idiopathic PD.

Morphometric study of myelinated fibers in human cervical spinal cord white matter

STUDY DESIGN

Using human autopsy spinal cord specimens, morphologic measurements of myelinated nerve fibers were performed, focusing on the regions that include the main white matter conduction paths. The hemilateral spinal cord morphology was also measured, and its relation with the component myelinated nerve fibers determined.

OBJECTIVES

To determine the relation between spinal cord transverse area in the normal lower cervical spine, the site most vulnerable to chronic compressive myelopathy, and myelinated nerve fibers.

SUMMARY OF BACKGROUND DATA

Considerable interindividual variation normally is observed in the morphology of the spinal cord transverse area. The influence of this variation on the composition of the white matter myelinated nerve fibers is obscure.

METHODS

The C7 segments from seven cadavers were resected, and from magnified photographs of paraffin-embedded specimens, the hemilateral spinal cord area and funicular area were measured. Nerve fiber morphology was measured using Epon-embedded specimens. Three regions that included the main conduction paths were sampled, and magnified photographs obtained. The nerve fiber transverse morphology was measured using the ellipse conversion method, and the myelinated nerve density and fiber area were determined.

RESULTS

Marked interindividual variations were found in both the hemilateral spinal cord transverse area and funicular area. A positive correlation was noted between the two, with the spinal cord transverse area large in the cases with a large funicular area. For fiber density and area, histograms were constructed that showed characteristic distribution patterns in each region. By dividing each region into two components (i.e., small- and large-diameter fibers), it was found that the interindividual variation in large-diameter fiber density was small, clarifying that the absolute number of large-diameter fibers compared to fiber density is more strongly dependent on the funicular area.

CONCLUSIONS

The absolute number of large-diameter myelinated fibers is smaller in cross-sections of thin as compared to those of thick spinal cord. When elucidating the pathophysiology of compressive myelopathy, it is necessary to study not only the circumstances surrounding the spinal cord, but this kind of factor intrinsic to the spinal cord itself.

Nerve conduction studies, skeletal muscle EMG, and sphincter EMG in multiple system atrophy

Although autonomic failure, parkinsonism, and cerebellar and pyramidal signs are well documented in multiple system atrophy, much less is known about the frequency and severity of involvement of the peripheral nervous system. The frequency and nature of peripheral nerve involvement has therefore been determined in 74 patients with multiple system atrophy using nerve conduction studies and skeletal muscle EMG. These findings were compared with those on sphincter EMG. Ninety per cent of the patients had an abnormal sphincter EMG, indicating denervation and reinnervation consistent with anterior horn cell loss in Onuf's nucleus, but only 40% had either abnormal nerve conduction studies (mixed sensorimotor axonal neuropathy in 17.5%) or abnormal skeletal muscle EMG (suggesting partial denervation in 22.5%). These data indicate a remarkable selective vulnerability of the anterior horn cells of Onuf's nucleus innervating external sphincter muscles relative to those supplying skeletal muscle in patients with multiple system atrophy. If this selective pattern of involvement can be explained it may be a clue to pathogenetic mechanisms in multiple system atrophy.

Age-related changes of the myelinated fibers in the human corticospinal tract: a quantitative analysis

A quantitative analysis was made of the myelinated fibers in the lateral corticospinal tract (LCST) at the levels of the 6th cervical, 7th thoracic and 4th lumbar spinal segments in 20 patients between 19 and 90 years old, and who died of non-neurological diseases. The diameter frequency histograms of myelinated fibers of LCST showed a bimodal pattern with a sharp peak of the small myelinated fibers and broad slope of the large myelinated fibers. The ratio of small fiber to large fiber densities was significantly higher in the 6th cervical (P < 0.05) and 4th lumbar segments (P < 0.01) than in the 7th thoracic segments. The density of small myelinated fibers was significantly lowered with advancing age (P < 0.05-0.001), while that of large myelinated fibers was not significantly decreased in the aged patients, although it showed a slight age-dependent declining tendency. Age-dependent decline of small fiber density was more prominent in the cervical and lumbar segments. Retraction of the axon-collaterals from large-diameter myelinated fibers, which are abundant in the cervical and lumbar segments, may contribute to the age-related diminution of the small myelinated fibers in the LCST.

Disease-specific patterns of neuronal loss in the spinal ventral horn in amyotrophic lateral sclerosis, multiple system atrophy and X-linked recessive bulbospinal neuronopathy, with special reference to the loss of small neurons in the intermediate zone

The ventral horn cells of the fourth lumbar segment were morphometrically analysed in six cases of amyotrophic lateral sclerosis (ALS; there common forms and three pseudopolyneuritic forms), six of multiple system atrophy (MSA) with autonomic failure, four of X-linked recessive bulbospinal neuronopathy (X-BSNP), and seven age-matched autopsy cases of non-neurological disorders. In the common form of ALS, large and medium-sized neurons of the medial and lateral nuclei were markedly lost; small neurons in the intermediate zone were slightly diminished but fairly well preserved. In the pseudopolyneuritic form of ALS, marked loss was present in the large and medium-sized neurons, and in the small neurons located in the intermediate zone as well. In the MSA, in contrast to ALS, there was a marked reduction in small neurons in the intermediate zone, and large and medium-sized neurons of the medial and lateral nuclei tended to be preserved. In X-BSNP, large and medium-sized neurons were almost completely lost and small neurons were also markedly depopulated. These findings indicated that the pattern of neuron loss in the ventral horn is distinct among these diseases depending on size, location and function of the ventral horn cell population. These disease-specific patterns of neuron loss suggest a difference in the process of neuronal degeneration of ventral horn cells among the disease examined.