Intranervous immunoglobulin deposits: an underestimated mechanism of neuropathy

There are several pathogenic mechanisms of peripheral nerve involvement in patients with monoclonal dysglobulinemia. Intranervous proliferation of malignant cells, immunoglobulin, or amyloid deposits in the endoneurial space can only be determined by examination of nerve biopsy specimens. We present clinical, electrophysiological, and histological data from seven patients whose polyneuropathy was induced by immunoglobulin deposits in the endoneurial space. As these lesions cannot be demonstrated on clinical and electrophysiological grounds, the indication for nerve biopsy derives from careful analysis of each patient presenting with a polyneuropathy and a monoclonal dysglobulinemia. To visualize and clearly characterize these deposits, electron microscopic examination is indispensable. Immunocytochemical methods using both light and electron microscopy for ultrastructural analysis are of great value. Demonstration of endoneurial immunoglobulin deposits may have major therapeutic consequences. Indeed, identification of these deposits prompted the use of aggressive treatment, which was quite effective in five of our seven patients.     

The persistence and possible externalization of axonal debris during Wallerian degeneration.

The sequence of changes in transected rat sciatic nerves were subjected to parallel ultrastructural and biochemical studies. Widespread granular disintegration of axoplasmic microtubules and neurofilaments occurred in the 24--72 hour interval following nerve transection. These changes were associated with a loss of neurofilament proteins and a marked enhancement of 53,000, 70--73,000 and 85,000 MW proteins in transected nerve. The emergence of prominent nerve proteins during the aftermath of axonal degeneration supports their derivation from axonal sources. These three proteins remained prominent components in transected nerves and comprised the major proteins found in 34-day transected nerves. Amorphous granular breakdown products from myelinated and unmyelinated nerve fibers were encountered with progressively decreasing frequency after 48 hours. This diminution of intracellular axonal debris was accompanied by the appearance and increasing prominence of amorphous granular deposits within the endoneurium of transected nerves. These endoneurial deposits became closely associated with collagen fibers and persisted as a prominent component in 34-, 80- and 120-day transected nerves. It is suggested that the amorphous endoneurial granular deposits arise in part from the externalization of granular axoplasmic breakdown products. Externalized axonal components could have important implications for tissue reaction to injury.     

Transport of epidurally applied horseradish peroxidase to the endoneurial space of dorsal root ganglia: a light and electron microscopic study

The route by which an epidurally applied macromolecule might reach the endoneurial space of spinal nerve roots was assessed with light and electron microscopy in a pig model established to explore the pathophysiology of disk herniation. Horseradish peroxidase (HRP) dissolved in saline was infused epidurally. Animals were sacrificed after 5 minutes (n = 5) or 30 minutes (n = 5). Two control animals received only a saline infusion and were sacrificed after 30 minutes. Nerve root specimens were collected, fixed, and exposed to the HRP substrate, 3.3'-di-amino-benzidine (DAB). The distribution of HRP reaction product in the nerve tissue was studied with light and electron microscopy. In 5-minute specimens, HRP was found in epidural and intradural vessel walls. At the nerve root level, HRP was detected in meningeal membranes but was not seen in periaxonal space. In addition to engaging the outer cell layers of the dorsal root ganglion (DRG) capsule, HRP was detected as a gradient among the peripherally located nerve cell bodies and sometimes among the emerging afferent axons. The 30-minute group demonstrated similar findings. The results confirm that HRP can reach the periaxonal spaces of lumbar DRG within 5 minutes after epidural application. Although the transport mechanism is not fully understood, the DRG may constitute an anatomical location allowing epidurally applied macromolecules entrance to the endoneurial space, either by direct diffusion or via vascular transport. The demonstrated transport route may have implications in the pathophysiology of sciatica in conjunction with lumbar disc herniation.     

Subperineurial space of the sural nerve in various peripheral nerve diseases

Summary The size of the subperineurial space of the sural nerve has been evaluated quantitatively in 69 cases of various peripheral nerve diseases and in controls. A significant increase was found in beriberi neuropathy (6 cases) and idiopathic polyradiculoneuropathy (9 cases) as compared with the control (8 cases). On electron microscopy a few macrophages, fibroblast processes, collagen fibrils with a diameter of 50 nm, microfibrils with a diameter of 8 nm, and amorphous material were observed in both the enlarged subperineurial space and the endoneurial intercellular space. They were less frequently observed in controls. No significant correlation was found between the size of subperineurial space and the density of myelinated fibers.     

The effect of combined neurolytic blocking agent 5% phenol-glycerol in rat sciatic nerve

Combined 5% phenol-glycerol has been used to treat cancer pain or spasticity and as sympathetic blocks. The major clinical problems have been the unpredictable effects on pain and on the duration of the blocks. Previously we have shown that intraneurally injected phenol induces haemorrhagic necrosis as well as dissolving of the nerve fibres. Glycerol, on the other hand, induces dispersion of nerve fibre debris into the endoneurium. We have now studied the effects of a combination of these two chemically different agents. The endoneurial and epineurial responses of rat peripheral nerve were followed after intraneural and perineural injections. Samples for electron microscopic and immunohistochemical studies were taken at 1–26 weeks after the injection. The intraneural phenol-glycerol injection resulted in gross endoneurial damage with partly or totally dissolved nerve fibres. Totally dissolved nerve fibres showed empty, collapsed basal lamina tubes and partly dissolved nerve fibres showed breaching of remaining degenerative debris into the endoneurial space. Axonal regeneration was delayed and was observed first after 2 weeks and it took 4 months before most of the nerve fibres were myelinated. The perineural injections resulted in partial subperineurial damage of the endoneurium morphologically similar to the results caused by the intraneural injection. An initial high accumulation of epineurial macrophages was noted at 1 and 2 weeks. An invasion of macrophages into the endoneurium occurred within 1 week after the intraneural and perineural injections and the number of endoneurial macrophages remained high for up to 6 months. The present study shows that glycerol added to phenol diminishes the necrotizing effect of phenol after an intraneural injection. Combined phenol-glycerol-induced nerve injury is reversible and the axons regenerate but residual morphological changes can be observed even after 6 months.     

IgG neuropathy: an immunoelectron microscopic study

There are many potential mechanisms of peripheral nerve impairment by a monoclonal IgG dysglobulinemia. In this study, using electron microscopy, we observed widening of the myelin lamellae comparable to that commonly described in IgM neuropathies with antimyelin-associated glycoprotein activity. Such features have yet to be described in IgG neuropathies. In addition, we observed deposits of a granular material in the interstitial tissue of the nerve. By immunoelectron microscopy, we demonstrated the presence of the IgG in the lesions of myelin and the endoneurial space. A direct link between monoclonal dysglobulinemia (regardless of type) and polyneuropathy should be confirmed by nerve biopsy, because the result may influence treatment.     

A study of the perineurium in peripheral nerve pathology

Summary The response of the perineurium to the following experimental systems was investigated by light and electron microscopy: nerve crush, cold lesion and microinjection of (a) histamine liberator, (b) potassium cyanide, (c) lysophosphatidyl choline (LPC). Where myelin breakdown occurred, lipid globules were seen within Schwann cells, macrophages and also perineurial cells. Where increased vascular permeability occurred, proteinaceous material leaked from endoneurial vessels into the endoneurial space and later appeared between perineurial laminae. It is suggested that the normal homeostatic function of the perineurium is extended in pathology to the removal of protein and lipid debris. In this way the perineurium contributes to the restoration of the normal microenvironment of peripheral nerve fibres.A synopsis of this paper was presented at the VIIth International Congress of Neuropathology, Budapest.     

Peripheral neuropathy in macroglobulinemia: incidence and antigen-specificity of M proteins

Peripheral neuropathy was found in 12 (46%) of 26 patients with macroglobulinemia. The neuropathy was subclinical in two. Anti-myelin-associated glycoprotein (MAG) activity was found in six (50%) patients with neuropathy. Sural nerve biopsies showed demyelination and IgM deposits on the myelin sheath. In one patient who had no anti-MAG activity, the serum IgM bound to peripheral myelin by indirect immunofluorescence and to several protein bands in peripheral nerve and other tissues by immunoblot. In the other five patients with neuropathy, we found no binding of M proteins to nerve components, but in three patients there were endoneurial IgM deposits in nerve biopsy. Peripheral neuropathy may be related to the antigen-specificity of M proteins.     

Immune-mediated neuropathy and myopathy in post-streptococcal disease: electron-microscopical, morphometrical and immunohistochemical studies.

A 22-year-old man suffered from a complete flaccid tetraparesis and an immune complex-mediated rapid progressive glomerulonephritis after group A streptococcal infection. Serum creatine kinase was excessively elevated and myoglobinuria occurred. Nerve conduction studies revealed evidence of axonal neuropathy. Recovery was satisfactory within 18 months. Sural nerve and peroneus muscle biopsies were performed in the 4th and 14th week of the disease. Light microscopy of the sural nerve showed an incipient axonal type of neuropathy in the first biopsy. Ultrastructurally, Wallerian degeneration and endoneurial inflammatory cells were present. In the muscle biopsy, few atrophic fibers and altered blood vessels without further anomalies were found. In the second sural nerve biopsy, macrophages were numerous, some of which were immunoreactive for HLA-DR, and only a few myelinated and some unmyelinated nerve fibers remained. Muscle fibers in the second biopsy showed high-grade atrophy and myofibrillar abnormalities. Immunohistochemistry revealed diffuse endoneurial immunoglobulin deposition in the first sample, while in the later biopsy specimen, deposits of IgG, and kappa and lambda light chains were visible in circumscribed endoneurial areas. Immune-mediated neuropathy and myopathy are not well-known complications of streptococcal disease. This is, to our knowledge, the first detailed report on morphological findings in muscle and nerve in such a disorder.     

Amyloid neuropathy: immunocytochemical localization of intra- and extracellular immunoglobulin light chains

Summary Sural nerve specimens from ten patients with amyloidosis (hereditary, associated with lymphoproliferative disorders, or of unknown origin) and peripheral neuropathy were investigated by immunohistochemistry at the light and electron microscopic level. Peroxidase-antiperoxidase and immunogold techniques were applied to glutaraldehyde-fixed, osmicated and epoxy-embedded tissue. In five cases, four of which associated with lymphoproliferative disorders, amyloid deposits strongly and exclusively reacted with antibodies to kappa or lambda light chains, respectively. By electron microscopy, bundles of immunogold-labelled amyloid fibrils could be identified in coated and uncoated single membrane-bound vesicles of endoneurial macrophages. Schwann cells did not contain intracellular amyloid but their processes were entangled in amyloid fibrils and their basement membranes were sometimes fused with the fibrillar masses. It is concluded that immunoglobulin light chains in AL (amyloid of immunoglobulin light chain origin) amyloidosis precipitate, forming amyloid fibrils, in the presence of, and presumably with the assistence of, endoneurial cells. Inefficiency of phagocytosis appears to be one of the major causes for the deleterious effects of amyloid.Supported in part by a grant from the Deutsche Forschungsgemeinschaft (FE 255/1/1) (CS). Presented in Part at the Fourth International Meeting of the Periveral Nerve Association of America, Halifax, July 19–23, 1988     

Comparative ultrastructural observations on peripheral nerve abnormalities in the late infantile,juvenile and late onset forms of metachromatic leukodystrophy

Summary The ultrastructural findings in nerve biopsies from two cases of late onset metachromatic leukodystrophy were compared with those in cases of late infantile and juvenile onset. Hypertrophic changes and regenerating clusters were more evident in the late onset cases, in which macrophages were less frequent, presumably reflecting the chronicity of the disorder in this form. Inclusions within Schwann cells and endoneurial macrophages were similar in all four cases. Myelin figures, in which the periodicity of major dense lines was 8 nm, were present in Schwann cells associated with myelinated axons. The electron lucent zones between the major dense lines were bisected by lines of lesser electron density. These inclusions were probably related to myelin breakdown. All other inclusions displayed a periodicity of 5.8 nm and consisted of zebra bodies, vacuoles containing irregularly orientated lamellar material and stacks of flattened discs. These inclusions represented the metachromatic sulphatide deposits. Occasional inclusion bodies were observed within axons.     

Gian axonal neuropathy--a generalized disorder of cytoplasmic microfilament formation.

Light and electron microscopy of a sural nerve biopsy obtained from a patient with giant axonal neuropathy revealed the presence of numerous axonal spheroids which were composed chiefly of neurofilaments. Large discrete masses of cytoplasmic microfilaments were also observed in endoneurial fibroblasts, endothelial cells, Schwann cells, perineurial cells and cultured skin fibroblasts. Neuronal degeneration in giant axonal neuropathy appears to be part of a generalized disorder of cytoplasmic microfilament formation.     

Amyloid neuropathy and multiple myeloma. Ultrastructural and immunopathological study of two cases

Report of 2 patients suffering from sensory peripheral neuropathy and multiple myeloma. In 1 case, peripheral neuropathy occurred several months before the appearance of multiple myeloma. A peripheral nerve biopsy exhibited numerous amyloid deposits within the endoneurium. Amyloid deposits have been estimated to occur in 15% of cases of multiple myeloma, but only 4 other detailed observations of amyloid deposits within the endoneurium have been reported in the literature. Other mechanisms might be involved since most peripheral neuropathies associated with multiple myeloma do not exhibit any amyloid deposits.     

Peripheral nerve pathological findings in familial amyloid polyneuropathy: a correlative study of proximal sciatic nerve and sural nerve lesions

To analyze the peripheral nerve pathological abnormalities in familial amyloid polyneuropathy, a correlative pathological study was carried out on the spinal nerve roots, proximal sciatic nerves, sural nerves, and brachial plexuses from 3 patients with the disease in Japan. The spinal nerve roots appeared to be unaffected except for amyloid deposition on the epineurium. In sciatic nerves and brachial plexuses the nerve lesions had a multifocal distribution, showing prominent interstitial edema in the endoneurium frequently adjacent to deposits of amyloid; in these regions the nerve fibers were severely depleted. A teased-fiber study revealed that segmental demyelination was the predominant type of nerve fiber abnormality. However, these findings were not seen in the sural nerves; instead a diffuse fiber loss with axonal degeneration was observed. It is suggested that multifocal lesions in the proximal portions of the long extremity nerves could summate distally to produce a symmetrical polyneuropathy in the disease. In addition to a space-occupying effect of amyloid deposits in the endoneurium, severe endoneurial edema associated with amyloid deposition in blood vessels and the endoneurial interstitium may induce ischemia in nerve fibers, thus causing the progressive polyneuropathy in this disorder.     

The experimental production of Renaut bodies

Renaut bodies are loosely-textured whorled, cell-sparse structures found in the subperineurial space of peripheral nerves. Although described in 1881, their significance is still debated. Rats were placed in wire-mesh cages for 4 days to 6 weeks and the lateral and medial plantar nerves were sequentially removed. The initial change was the presence of endoneurial edema which dissected and displaced nerve fibers producing an endoneurial cleft. With the influx of fibroblasts, these clefts became discretely separated by circumferentially oriented processes. Over time the clefts enlarged and became filled with loosely-textured amorphous and fibrillar material as well as collagen. The Renaut bodies ranged from 15 to 80 microns in diameter. In this model the Renaut bodies formed at the maximum site of compression of the lateral plantar nerve. The fibroblasts appeared to be derived from the endoneurial connective tissue and were not the result of degenerating endoneurial structures. Renaut body formation was independent of axonal degeneration. The present study strongly suggests that Renaut bodies are a response to repeated mechanical stress.     

Chronic constriction model of rat sciatic nerve: nerve blood flow,morphologic and biochemical alterations

We evaluated the nerve blood flow (NBF), light and electron microscopy, and adrenergic innervation of rat sciatic nerve at 2–45 days after the application of four loose ligatures. Ischemia developed at the lesion edge, creating an endoneurial dam. Calcitonin gene-related peptide, norepinephrine and NBF were increased within the lesion. Morphologic alterations consisted of early endoneurial edema, followed by myelinated fiber degeneration, with relative sparing of small myelinated and unmyelinated nerve fibers, and leukocyte adhesion to microvessels. Axonal degeneration predominated over demyelination. At 45 days, profuse regeneration of small myelinated fibers was seen. The mechanism of lesional sensitization is discussed. Received: 30 May 1996 / Revised, accepted: 13 August 1996     

Cellular uptake of exogenous horseradish peroxidase in mouse peripheral nerve

Summary Horseradish peroxidase (HRP) was given to adult normal mice either intravenously or locally around the sciatic nerve. After varying time intervals the animals were sacrificed and fixed by whole body perfusion. The sciatic nerve was sampled and the distribution of peroxidatic activity was studied by light and electron microscopy.After both types of HRP administration the tracer was rapidly taken up by epi- and endoneurial cells with the ultrastructural features of macrophages. When increasing doses of HRP were injected intravenously a diffuse endoneurial extravasation was observed 30 min after the injection.It is concluded that a passage of HRP takes place over some endoneurial vessels. The nature and significance of endoneurial macrophages are discussed.     

Morphometric changes in sympathetic nerve fibres in diabetes

A morphometric study was carried out on electron micrographs of lumbar sympathetic nerve fibres surgically removed from 12 patients with arteriosclerosis obliterans: 4 diabetics, 4 non-diabetics and 4 subjects with glucose intolerance. In patients with diabetes and glucose intolerance a significant decrease in the percent area fraction of unmyelinated axons and an increase in the percent area fraction of the endoneurial space were demonstrated.     

Collagen content in human ulnar nerve

Summary A quantitative analysis of ulnar nerve collagen in the arm and forearm was undertaken in nine subjects. While endoneurial collagen was found to be significantly increased within the cubital tunnel, extrafascicular collagen did not increase at the elbow except in two nerves showing fusiform enlargements. Renaut bodies increased in frequency at sites of high endoneurial collagen content. Morphological determinations of cross-sectional area along the ulnar nerve did not correlate with quantitative collagen data.