Amyotrophic lateral sclerosis with ophthalmoplegia and multisystem degeneration in patients on long-term use of respirators

Summary We describe two patients with sporadic amyotrophic lateral sclerosis (ALS), who had developed progressive external ophthalmoplegia of a predominantly supranuclear type while they survived on respirators, and displayed histopathological abnormalities both typical and atypical of ALS. Patient 1 was a 43-year-old man with ALS of 5-year duration, who had initially exhibited fulminant ALS, and remained on a respirator for 4 years. Patient 2 was a 51-year-old man with ALS of 13-year duration, who remained on a respirator for 8 years. Both patients died in a totally locked-in state. Autopsy of both patients revealed not only histopathological abnormalities consistent with ALS, but also multisystem degeneration which involved the pontine tegmentum, substantia nigra, Clarke's dorsal nuclei and spinocerebellar tracts. In addition, Patient 2 displayed intracyto-plasmic neuronal basophilic inclusion bodies which exhibited marked immunoreactivity to anti-ubiquitin antibodies. Our case reports indicate that the longer survival which is possible through the use of respirators may make one subgroup of ALS patients prone to develop atypical clinical and neuropathological features which are not observed during the natural cours of ALS.Supported by a Grant-in-Aid from the Research Committee of CNS Degenerative Diseases, the Ministry of Health and Welfare of Japan, and by a Grant from Nihon University School of Medicine, Tokyo     

Pursuit of the origin of the large myelinated fibers of the anterolateral funiculus in the spinal cord in humans in relation to the pathomechanism in amyotrophic lateral sclerosis

To determine the origin of the large myelinated fibers in the anterolateral funiculus (ALF) in the spinal cord of humans, myelinated fibers in the ALF of the mid-cervical spinal cord were examined quantitatively. Five groups of subjects were examined, consisting of control subjects, patients with cerebral lesions and showing complete degeneration of the unilateral/bilateral pyramis of the medulla oblongata, those with lesions of the pontine tegmentum, those with lesions of the lower cervical spinal cord, and those with thoracic/lumbar lesions. The results indicate that the large myelinated fibers in the ALF of the mid-cervical spinal cord of humans originate from the tegmentum of the brain stem and the lower cervical spinal cord, and not from the cerebrum, or the thoracic or lumbar spinal cord. Thus, they are descending fibers from the brain stem tegmentum and ascending fibers from the lower cervical cord, and not corticospinal tracts or long-ascending fibers from the thoracic or lumbar spinal cord. The origin of the large myelinated fibers in the ALF of the spinal cord in humans, the number of which was severely decreased in patients with amyotrophic lateral sclerosis, is considered to be the long-descending neurons in the brain stem tegmentum and the propriospinal neurons in the spinal cord. Received: 23 December 1998 / Revised, accepted: 29 March 1999     

The corticospinal tract of amyotrophic lateral sclerosis--a morphometric analysis of the myelinated fibers]

The myelinated fibers in the lateral corticospinal tract at the C6, T7, L4 levels in amyotrophic lateral sclerosis (ALS) and control cases were morphometrically examined. ALS cases consisted of 6 males and 2 females with ages ranging between 48 and 85 years, and were all the common or bulbar form in clinical manifestation. As for controls, 10 cases who died of non-neurological diseases, with age ranging 36 to 90 years were served. The population and the diameter profile of the myelinated fibers in the corticospinal tract of the C6, T7, L4 levels were measured by the method previously described and expressed as number per mm2. In control subjects, fiber-size histograms of myelinated fibers showed a bimodal pattern with a sharp peak of small fibers (less than 7.28 microns) and a broad peak of large fibers (greater than or equal to 7.28 microns) in all the spinal levels. In ALS cases, large myelinated fibers were predominantly diminished in number, a small myelinated fibers were also decreased in some cases. The degree of fiber loss was extremely variable among cases; well populated in large fibers in some cases. As for the rostral caudal distribution of myelinated fiber loss, a caudally-accentuated fiber loss particularly in large fiber was seen in some of the cases. The topographical distribution of fiber loss in the horizontal plane of the corticospinal tract in ALS did not show a distinctive pattern.     

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<0.050.001), 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.Part of this work was supported by grants from the Ministry of Welfare and Health of Japan, and a grant from Uehara Memorial Research Foundation     

The ultrastructure of intramuscular nerves in amyotrophic lateral sclerosis

Summary Muscle biopsies of 11 patients suffering from amyotrophic lateral sclerosis (ALS) were examined and the i.m. nerves found in seven of them were examined by electron microscopy. In atrophied muscles there was a marked decrease of myelinated fibers. The ultrastructure of the remaining myelinated axons showed changes in the neurofilaments, mitochondria, and vesicles. There was a decrease in the number of unmyelinated fibers as well as the myelinated fibers. Occasionally, there was an increase of unmyelinated fibers containing small fine axons. There were corpora amylacea in unmyelinated axons and banded structures in the extraccllular area of the Schwann cells of the unmyelinated fibers. Some of these findings were considered as the ultrastructural features of degeneration and regeneration in i.m. nerves of motoneurons in ALS.Supported in part by a Research Grant for Intractable Diseases from the Ministry of Health and Welfare of Japan     

Pathology of myelinated fibers in cervical and lumbar ventral spinal roots in amyotrophic lateral sclerosis

Pathological alterations were evaluated by morphometry and by a teased-fiber study on the 6th cervical (C6) and the 4th lumbar (L4) ventral spinal roots of cases of amyotrophic lateral sclerosis (ALS). The large-diameter myelinated fibers were severely affected in both spinal segments. However, small-diameter myelinated fibers were numerically well preserved. The number of large fibers in C6 and L4 ventral roots was strongly correlated to the strength of muscles innervated by C6 or L4 segments. There was no correlation of the number of small fibers with muscle strength. Teased fiber studies revealed a marked increase in the incidence of fibers showing axonal degeneration. Fibers considered to be regenerative were rarely observed. These observations suggest that large myelinated fibers, which correspond to -motoneuron fibers, are selectively affected, and that small myelinated fibers, which are considered to correspond to γ-motoneuron fibers, are preserved to some extent in the C6 and L4 ventral spinal roots in ALS.     

Amyotrophic lateral sclerosis. Lack of central chromatolytic response of motor neurocytons corresponding to active axonal degeneration

Ventral spinal roots and anterior horn cells in the lateral nuclear group of the fourth lumbar segment from 21 patients with amyotrophic lateral sclerosis (ALS) and 23 control patients were morphometrically analyzed. The number of large myelinated fibers was remarkably decreased, while small myelinated fibers were well preserved. The population of large myelinated fibers significantly correlated with the population of anterior horn cells. Numerous axonal degenerations were observed in the ventral spinal roots of patients with ALS, even in patients with severe loss of neurons and axons. In spite of this high frequency of active axonal degeneration, the incidence of central chromatolysis of anterior horn cells remained at the control level.     

α-Synuclein in motor neuron disease: an immunohistologic study

-Synuclein (ASN) has been implicated in neurodegenerative disorders characterized by Lewy body inclusions such as Parkinsons disease and dementia with Lewy bodies. Lewy body-like inclusions have also been observed in spinal neurons of patients with amyotrophic lateral sclerosis (ALS) and reports suggest possible ASN abnormalities in ALS patients. We assessed ASN immunoreactivity in spinal and brain tissues of subjects who had died of progressive motor neuron disorders (MND). Clinical records of subjects with MND and a comparison group were reviewed to determine the diagnosis according to El-Escariol Criteria of ALS. Cervical, thoracic and lumbar cord sections were stained with an antibody to ASN. A blinded, semiquantitative review of sections from both groups included examination for evidence of spheroids, neuronal staining, cytoplasmic inclusions, anterior horn granules, white and gray matter glial staining, corticospinal tract axonal fiber and myelin changes. MND cases, including ALS and progressive muscular atrophy, displayed significantly increased ASN staining of spheroids (P0.001), and glial staining in gray and white matter (P0.05). Significant abnormal staining of corticospinal axon tract fibers and myelin was also observed (P0.05 and 0.01). Detection of possible ASN-positive neuronal inclusions did not differ between groups. Significant ASN abnormalities were observed in MND. These findings suggest a possible role for ASN in MND; however, the precise nature of this association is unclear.     

Clarke's column in sporadic amyotrophic lateral sclerosis

Summary Histological, ultrastructural and morphometrical observations on Clarke's column were carried out in 18 patients with sporadic amyotrophic lateral sclerosis (ALS) and 15 age-matched control subjects. Of the 18 ALS patients 6 had been on a respirator before death. Bunina bodies were found in the neuronal cytoplasm in 7 of the 12 non-respirator-supported ALS patients and in 3 of the 6 respirator-supported patients. The number of spheroids was significantly higher in the non-respirator-supported patients (P<0.01) than in the control subjects; however, the number in the respirator-supported patients was about equal to that in the controls. The number of neurons in Clarke's column in the non-respirator-supported ALS patients was not reduced, but in the respirator-supported patients they tended to disappear with time after respiratory support. These findings suggest that Clarke's column neurons are also involved primarily in the disease process in sporadic ALS. However, they may begin to disappear only after the patients require respiratory support.Supported in part by a research grant for CNS degenerative diseases from the Ministry of Health and Welfare, Japan     

A clinicopathological study of the somatic motor efferents in the pseudopolyneuritic form of amyotrophic lateral sclerosis

Histopathology of the somatic motor efferents of three cases with pseudopolyneuritic from of amyotrophic lateral sclerosis (ALS) was analyzed, and the results were correlated with the clinical symptoms. The population of myelinated fibers in the lateral corticospinal tract at the thoracic segment, and in the fourth ventral roots, and motor neurons in the fourth ventral horns were morphometrically quantified. The patients were two males and one female ranging in age from 43 to 67 years, and showed a clinical course of 1.8 to 9.5 years. All three cases did not show any pyramidal sign nor spasticity but showed an extensive leg involvement, particularly the distally accentuated muscular weakness with depressed deep tendon reflexes. The clinical manifestations were consistent with the pseudopolyneuritic form of ALS. Fiber size profile of the myelinated fibers in the lateral corticospinal tracts at T7 segments and L4 lumbar ventral roots were estimated on the epon-embedded transverse sections as previously described (Sobue et al, 1981). Number and size distribution of anterior horn cells in the L4 segments were measured on 300-500 consecutive 10 microns-thick paraffin sections stained with Klüver-Barrera technique, using a TGZ-3 particle size analyzer (Zeiss). The location of the remained anterior horn cells was also quantitatively estimated. Three cases with common form of ALS and three control cases were analyzed in the same manner. The large myelinated fibers in the lateral corticospinal tract were extensively and predominantly depleted in all three cases. The small myelinated fibers were also depopulated but in lesser degree. The mode of these myelinated fiber loss was almost compatible with those in common form of ALS.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study of three patients with amyotrophic lateral sclerosis and a polyneuropathy resembling CIDP

We report three patients with a syndrome that fulfilled clinical and laboratory criteria for definite chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who failed immunosuppressive treatment and eventually developed progressive amyotrophic lateral sclerosis (ALS). Mean disease duration was 23 months (13-38) before death. Two patients had a family history of ALS without mutations of the SOD1 gene. Postmortem examination in one patient showed an endoneurial infiltration of mononuclear cells in lumbar roots and distal and proximal peripheral nerves, mainly around myelinated fibers, with demyelination and axonal loss, consistent with CIDP. The spinal cord revealed severe neuronal loss in the anterior horn, axonal loss in the corticospinal tract, and large numbers of phagocytes in the anterior and lateral tracts, indicative of ALS. Whether demyelinating polyneuropathy was coincident with ALS or was a cause or consequence of motor neuron degeneration in these patients remains to be elucidated. This unusual combination may provide an important clue in elucidating the pathogenesis of ALS in some patients.     

The intermediolateral nucleus in sporadic amyotrophic lateral sclerosis

Summary Histological and morphometrical observations of the intermediolateral nucleus (IML) at the levels of the upper and lower thoracic segments (T2 and T9) were carried out in 18 patients with sporadic amyotrophic lateral sclerosis (ALS) and 15 age-matched control subjects. Of the 18 ALS patients 6 had been on a respirator before death. No Bunina bodies were found in the IML neurons in either the ALS patients or the control subjects. Only a small number of spheroids were encountered rarely in the IML in both the patients and controls. The number of neurons in the IML in the non-respirator-supported ALS patients were reduced at T2, but well preserved at T9 compared with the control subjects. In the respirator-supported ALS patients, there was a marked reduction of IML neurons at both T2 and T9. Considering the absence of direct synaptic contacts with anterior horn cells, these neurons, without the formation of Bunina bodies, appeared to be involved primarily in the disease process in sporadic ALS.Supported in part by a research grant for CNS degenerative diseases from the Ministry of Health and Welfare, Japan     

Morphometry of the degenerative process in the hypoglossal nerves in amyotrophic lateral sclerosis

Summary The peripheral hypoglossal nerves in 13 cases of amyotrophic lateral sclerosis (ALS) and five control cases were examined using morphometrical methods to demonstrate the degenerative process of motor nerve degeneration. The total number of myelinated fibers and their histograms were analyzed according to the degree of severity of the degeneration. Reduction of the total number of myelinated fibers in ALS hypoglossal nerves were graded in three groups: mild 65%–75%, moderate 50%–65% and severe 30%–50% of the myelinated fibers in controls. Each histogram of the remaining myelinated fibers showed different patterns corresponding to the degree of the degeneration and disclosed that the progressive reduction of large myelinated fibers was the fundamental change. Small myelinated fibers were not reduced, but increased, especially in the group with a moderate grade of degeneration. In plastic section, there were clusters of regenerated myelinated fibers. The transient increase of small myelinated fibers may be a reflexion of myelinated fiber regeneration during the progressive degenerative process of the motor neurons. The correlation between the degree of severity of the hypoglossal nerve degeneration and the atrophy of the tongue muscle and the duration of bulbar symptoms was examined and discussed.Supported by grant from the Ministry of Health and Welfare of Japan (Research project of progressive degenerative neurological disease)     

Cerebrospinal fluid (CSF) findings in amyotrophic lateral sclerosis

Summary The cerebrospinal fluid (CSF) was examined in 90 amyotrophic lateral sclerosis (ALS) patients and in 50 age-matched normal controls. Total protein concentration was significantly higher in ALS patients than in normal controls. CSF IgG and albumin, quantitatively determined by single radial immunodiffusion, were significantly increased in ALS. No difference in serum concentrations was observed between ALS patients and normal controls. On isoelectric focusing a clear-cut fingerprint pattern was observed in 11 of 12 cases. These findings support the hypothesis that blood-brain barrier damage occurs in ALS. The finding of a higher mononuclear cell count in young ALS patients is briefly discussed in the light of the hypothesis that an exogenous agent might be of some relevance in pathogenesis. An alteration of at least one of the CSF parameters considered was found in 45.5% of ALS cases.

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Zusammenfassung In 90 Fällen von amyotrophischer Lateralsklerose und bei 50 auch im Alter entsprechenden Kontrollen wurde der Liquor untersucht. Der Eiweißgehalt war bei den Patienten mit ALS signifikant höher als bei den Kontrollen. Die Albuminfraktion und das IgG, die mit Immunodiffusionsmethoden quantitativ bestimmt wurden, waren bei der ALS im Liquor signifikant erhöht, während sie sich im Serum gleich wie bei den Kontrollfällen verhielten. Bei der isoelektrischen Fokusierung ließ sich ein eindeutiges Finger-print-pattern in elf von zwölf Fällen beobachten. Diese Befunde sprechen dafür, daß bei der ALS eine Störung der Blut-Hirnschranke vorliegt. Es wird kurz auf die Beobachtung einer vermehrten Zahl mononukleärer Zellen bei jungen Patienten mit ALS eingegangen und im besonderen die Frage diskutiert, in wieweit ein exogenes Agents in der Pathogenese eine Rolle spielen könnte. Mindestens eines der obern erwähnten Parameter war bei 45% aller ALS Fälle im Liquor verändert.

     

A comparative study between amyotrophic lateral sclerosis patients with and without mechanical ventilation

Fifty-three patients with amyotrophic lateral sclerosis (ALS) were examined as to duration of illness, cause of death and need for respirator assistance. In 47 patients with ALS, respiratory failure is the most common cause of death accounting for 62% of all fatalities. Eleven patients with mechanical ventilation died of pneumonia and respiratory failure in four cases, atelectasis, gastrointestinal bleeding and asphyxia in one. Thirteen of 53 patients with ALS required mechanical ventilation. Six cases were put on a volume-limited respiratory or a pressure-limited respirator with O2 blender, and seven cases were put on a pressure-limited respirator only, which was unable to control oxygen concentration. As to the duration of their illness, patients with mechanical ventilation survived significantly longer than those without mechanical ventilation, so patients using a respirator could expect to live significantly longer than those without one. Patients using a volume limited respirator or a pressure-limited respirator with O2 blender had significantly longer duration of mechanical ventilation than those using a pressure-limited respirator only. It is concluded that a volume-limited respirator or a pressure-limited respirator with O2 blender is useful, if mechanical ventilation is needed, for ALS patients presenting with respiratory failure.     

Cutaneous somatic and autonomic nerve TDP-43 deposition in amyotrophic lateral sclerosis

Objective

To evaluate the involvement of the sensory and autonomic nervous system in amyotrophic lateral sclerosis (ALS) and to determine whether TDP-43/pTDP-43 deposits in skin nerve fibers signify a valuable biomarker for ALS.

Methods

Eighteen patients with ALS and 18 age- and sex-matched control subjects underwent physical examinations, in addition to donating skin biopsies from the distal leg. The density of epidermal, Meissner’s corpuscle (MC), sudomotor, and pilomotor nerve fibers were measured. Confocal microscopy was used to determine the cutaneous somatic and autonomic nerve fiber density and TDP-43/pTDP-43 deposition.

Results

Intraepidermal nerve fiber density (IENFD) was reduced in individuals with ALS (P?<?0.001). MC density (MCD) (P?=?0.001), sweat gland nerve fiber density (SGNFD) (P?<?0.001), and pilomotor nerve fiber density (PNFD) (P?<?0.001) were all reduced in ALS patients. The SGNFD correlated with the small-fiber neuropathy Symptoms Inventory Questionnaire (SFN-SIQ), VAS and age. The SFN-SIQ was higher in ALS with sensory symptoms than without sensory symptoms (P?=?0.000). Furthermore, the SFN-SIQ was higher in ALS with autonomic symptoms than without autonomic symptoms (P?=?0.002). SFN-SIQ was higher in ALS patients that were pTDP-43 positive than pTDP-43 negative (P?=?0.04), respectively.

Conclusions

We established in the peripheral nervous system that higher SFN-SIQ and VAS was involved in ALS, indicating the loss of SGNF. The deposition of TDP-43/pTDP-43 in ALS nerve fibers may indicate an important role in the underlying pathogenesis of ALS. This observation might be used as a potential biomarker for diagnosing ALS.

     

Changes of unmyelinated nerve fibers in sural nerve in amyotrophic lateral sclerosis,Parkinson’s disease and multiple system atrophy

Quantitative changes in unmyelinated nerve fibers (UMNFs) of sural nerves in patients of amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and multiple system atrophy (MSA) were evaluated using autopsy materials whose pathological diagnosis had been confirmed by careful postmortem examinations. Ordinary ALS cases demonstrated no involvement in cutaneous UMNFs; however, the patients with long survival due to the application of ventilatory support showed bimodality in UMNF diameter histograms, and a patient with involvement of systems other than motor pathways showed an abnormal value in two indices: a low percentage of subunits containing axon(s) and a high mean number of Schwann cell profiles per axon. A significant reduction of the mean value of UMNF density (21%) was found in PD patients. Because the density of myelinated nerve fibers did not show any significant decrease as compared with age-matched controls, the change of nerve fibers in peripheral nervous system was considered to be confined to UMNFs in PD. Elderly PD cases showed enhanced changes in the ageing process, as expressed by the two indices described above. In MSA, the mean value of UMNF density was significantly decreased (23%), and this decrease almost paralleled that of myelinated nerve fiber density. Abnormal values for the two indices described above were found and two out of four cases demonstrated bimodality in the diameter histogram of UMNFs. Unlike MSA, ALS and PD have not been included in the disorders with cutaneous UMNF involvement. Our results supply the first evidence of morphological changes in cutaneous UMNFs in PD cases. In ordinary ALS cases, the emergence of such morphological changes is suggested in cases with long survival. Received: 7 November 1994 / Revised: 1 March 1995 / Accepted: 1 August 1995     

Hyposensitivity of peripheral α-adrenoceptors in respiratordependent amyotrophic lateral sclerosis assessed by intravenous norepinephrine infusion

Intravenous norepinephrine infusion test was performed in eight patients with amyotrophic lateral sclerosis (ALS) supported by respirators and nine control subjects, to examine -adrenoceptor function of peripheral resistant blood vessels. Baseline plasma norepinephrine concentrations in ALS patients were significantly higher than those in control subjects, indicating basal sympathetic hyperactivity (normal 218.2 ± 59.7 pg/ml; ALS 450.0 ± 288.4 pg/ml). The stimulus-response curves in the patients were similar to those in control subjects, and there were no significant differences between mean gains of the stimulus—response curves in both groups (normal 18.7 ± 5.5; ALS 15.2 ± 11.2). However, three ALS patients, two of whom had circulatory fluctuation and sympathetic hyperactivity, revealed lower gain levels than the mean minus 2 SD in control subjects (4.7, 1.1 and 3.7). This indicates hyposensitivity or down-regulation of the -adrenoceptor function of peripheral blood vessels in these ALS patients. For early detection of sympathetic hyperactivity and prediction of circulatory collapse, it would be useful to measure the plasma norepinephrine concentration and the gain of the norepinephrine infusion curve in respirator-dependent ALS patients.     

Increased variability of axonal excitability in amyotrophic lateral sclerosis

Objective

Amyotrophic lateral sclerosis (ALS) is characterised by the increased excitability of motoneurons and heterogeneous loss of axons. The heterogeneous nature of the disease process among fibres may show variability of excitability in ALS.

Methods

Multiple nerve excitability tests were performed in 28 ALS patients and 23 control subjects, by tracking at the varying threshold levels (10%, 20%, 40% and 60% of maximum amplitudes).

Results

In normal controls, excitability measures at low target levels have the following characteristics compared to those at high target levels: longer strength–duration time constant, greater threshold reduction during depolarising currents and smaller threshold increase to hyperpolarising currents. ALS patients had less clear amplitude dependency of the parameters than the controls, indicating variability of axonal excitability. Three ALS patients demonstrated greater target-amplitude-dependent threshold changes in threshold electrotonus than controls, suggesting selective axonal hyperexcitability.

Conclusions

Some of the ALS patients had variable axonal excitability at different target amplitudes, suggesting preferential hyperexcitability in the axons with low target amplitude levels.

Significance

Variable membrane potentials of motor axons in ALS may be assessed by recording excitability testing at different target amplitude levels.     

Licht- und elektronenmikroskopische sowie cytometrische Untersuchungen an peripheren Nerven beim Morbus Tangier

Summary A sural nerve biopsy was performed in a 55-year-old male patient with Tangier disease (familiallipoprotein deficiency). Light-microscopy showed an increase in the endoneural connective tissue and a loss of nerve fibers indicating a chronic peripheral neuropathy. Electron-microscopy revealed an accumulation of lipid droplets within Schwann cells of myelinated and unmyelinated nerve fibers. When compared with age-matched controls the myelinated fiber density was reduced with a relative preponderance of small myelinated fibers. In addition, distributional cytometric studies of nerve vibers in relation to the perineurium and endoneurial capillaries showed: Contrary to 4.6–7.5 m thick nerve fibers, which accumulated in the center of the nerve fascicle, small (0.5–4.5 m) and large (7.6–10.0 m) fibers lay nearby the perineurium. The measured increase in small myelinated nerve fibers around endoneurial capillaries may be explained as a sign of regeneration.