Chronic idiopathic ataxic neuropathy

Sensory neuronopathies, diagnostic criteria and causes

PURPOSE OF REVIEW

To stress on the diagnostic strategy of sensory neuronopathies (SNN), including new genes and antibodies.

RECENT FINDING

SNN involve paraneoplastic, dysimmune, toxic, viral and genetic mechanisms. About one-third remains idiopathic. Recently, new antibodies and genes have reduced this proportion. Anti-FGFR3 and anti-AGO antibodies are not specific of SNN, although SNN is predominant and may occur with systemic autoimmune diseases. These antibodies are the only marker of an underlying dysimmune context in two-thirds (anti-FGFR3 antibodies) and one-third of the cases (anti-AGO antibodies), respectively. Patients with anti-AGO antibodies may improve with treatment, which is less clear with anti-FGFR3 antibodies. A biallelic expansion in the RFC1 gene is responsible for the cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) in which SNN is a predominant manifestation. Most of the patients have an adult onset and are sporadic. The RFC1 mutation may represent one-third of idiopathic sensory neuropathies. Finally, the criteria for the diagnosis of paraneoplastic SNN have recently been updated.

SUMMARY

The diagnostic of SNN relies on criteria distinguishing SNN from other neuropathies. The strategy in search of their cause now needs to include these recent findings.

Investigation of nerve fibers in the skin by biopsy: technical aspects, indications, and contribution to diagnosis of small-fiber neuropathy

Skin biopsy with investigation of small-diameter nerve fibers in human epidermis and dermis has been proven to be a useful method for confirming small-fiber neuropathy. In medical practice, small-fiber neuropathy is increasingly recognized as a leading cause of neuropathic pain. It is a prevalent complaint in medical offices, brought by patients often as a “painful burning sensation”. The prevalence of neuropathic pain is high in small-fiber neuropathies of different etiologies, especially in the elderly; 7% of population in this age group present peripheral neuropathy. Pain and paresthesia are symptoms which might cause disability and impair quality of life of patients. The early detection of small-fiber neuropathy can contribute to reducing unhealthy lifestyles, associated to higher incidence of the disease.

Distal symmetric polyneuropathy phenotype in patients with sensory neuronopathy at the time of electrodiagnosis

INTRODUCTION/AIMS

It is unknown how often patients with sensory neuronopathy (SNN) present with a distal symmetric polyneuropathy (DSP) phenotype. In these cases, electrodiagnostic testing may discriminate SNN with a DSP phenotype from DSP.

METHODS

We reviewed the records of patients who met SNN diagnostic criteria between January 2000 and February 2021 and identified patients with a DSP phenotype at the time of electrodiagnosis.

RESULTS

Sixty-two patients fulfilled SNN diagnostic criteria. At symptom onset, 20 (32.2%) patients presented with distal symmetric sensory symptoms limited to the feet. However, most progressed rapidly over 6 months or developed asymmetric symptoms. At the time of electrodiagnosis, only seven (11.3%) patients had a DSP phenotype. Of these seven patients, four had cerebellar ataxia with neuropathy and vestibular areflexia syndrome, one had vitamin B₆ deficiency, one was thought to be alcohol-induced, and one was idiopathic.

DISCUSSION

Patients with SNN rarely present with a DSP phenotype at the time of electrodiagnosis. The finding that one third of cases resemble DSP at onset highlights the importance of clinical monitoring. In patients with a DSP phenotype, the presence of ataxia at onset or significant progression within 6 months may suggest the possibility of SNN and should prompt additional investigations, such as electrodiagnosis.

Sensory neuronopathies: A case series and literature review

Sensory neuronopathies are heterogeneous disorders of dorsal root ganglia. The clinical and laboratory features in a single-centre series, including response to treatment and outcome have been described. They retrospectively included 54 patients meeting Camdessanché et al (2009) criteria for sensory neuronopathy. The patients were classified according to their likely aetiology and analysed their demographic, clinical, neurophysiological, histological and spinal MRI features. The outcome with the modified Rankin Scale (mRS) was evaluated, and the response to treatment was assessed. About 54 patients were included (18 male; median age 54.5 years). The most common initial symptoms were hypoaesthesia, paraesthesia, ataxia and pain. Half of patients had a slow onset, greater than 12 months before seeing a neurologist. The aetiology as possibly inflammatory (meaning nonspecific laboratory evidence of immune abnormality) in 18 patients (33%), paraneoplastic 8 (15%), autoimmune 7 (13%) and idiopathic 6 (11%) was classified. About 31 patients received immune therapy of which 11 (35%) improved or stabilised. Corticosteroids were the most used treatment (24 patients) and cyclophosphamide had the highest response rate (3/6, 50%). At the final follow up (median 24 months) 67% had mRS ≥3 and 46% mRS ≥4, including 15% who died. Worse outcome was associated with generalised areflexia and pseudoathetosis by logistic regression, and with motor involvement and raised CSF protein by univariate analysis. Sensory neuronopathies caused severe disability, especially in patients with generalised areflexia and pseudoathetosis. Of those without an obvious cause, most had some evidence of dysimmunity. Some patients had a positive response to immunotherapy, but rarely enough to improve disability much.

Reorganization of motor modules for standing reactive balance recovery following pyridoxine-induced large-fiber peripheral sensory neuropathy in cats

Task-level goals such as maintaining standing balance are achieved through coordinated muscle activity. Consistent and individualized groupings of synchronously activated muscles can be estimated from muscle recordings in terms of motor modules or muscle synergies, independent of their temporal activation. The structure of motor modules can change with motor training, neurological disorders, and rehabilitation, but the central and peripheral mechanisms underlying motor module structure remain unclear. To assess the role of peripheral somatosensory input on motor module structure, we evaluated changes in the structure of motor modules for reactive balance recovery following pyridoxine-induced large-fiber peripheral somatosensory neuropathy in previously collected data in four adult cats. Somatosensory fiber loss, quantified by postmortem histology, varied from mild to severe across cats. Reactive balance recovery was assessed using multidirectional translational support-surface perturbations over days to weeks throughout initial impairment and subsequent recovery of balance ability. Motor modules within each cat were quantified by non-negative matrix factorization and compared in structure over time. All cats exhibited changes in the structure of motor modules for reactive balance recovery after somatosensory loss, providing evidence that somatosensory inputs influence motor module structure. The impact of the somatosensory disturbance on the structure of motor modules in well-trained adult cats indicates that somatosensory mechanisms contribute to motor module structure, and therefore may contribute to some of the pathological changes in motor module structure in neurological disorders. These results further suggest that somatosensory nerves could be targeted during rehabilitation to influence pathological motor modules for rehabilitation.NEW & NOTEWORTHY Stable motor modules for reactive balance recovery in well-trained adult cats were disrupted following pyridoxine-induced peripheral somatosensory neuropathy, suggesting somatosensory inputs contribute to motor module structure. Furthermore, the motor module structure continued to change as the animals regained the ability to maintain standing balance, but the modules generally did not recover pre-pyridoxine patterns. These results suggest changes in somatosensory input and subsequent learning may contribute to changes in motor module structure in pathological conditions.

Sensory Polyneuropathies

PURPOSE OF REVIEW

This article describes the methods of diagnosis and management of the sensory-predominant polyneuropathies. To simplify the approach to this category of patients, sensory-predominant polyneuropathies are divided broadly into either small fiber (or pain-predominant) neuropathies and large fiber (or ataxia-predominant) neuropathies, of which the sensory neuronopathies (dorsal root ganglionopathies) are highlighted.

RECENT FINDINGS

Physicians can now easily perform skin biopsies in their offices, allowing access to the gold standard pathologic diagnostic tool for small fiber neuropathies. Additional diagnostic techniques, such as corneal confocal microscopy, are emerging. Recently, small fiber neuropathies have been associated with a broader spectrum of diseases, including fibromyalgia, sodium channel mutations, and voltage-gated potassium channel antibody autoimmune disease.

SUMMARY

Despite advances in diagnosing small fiber neuropathies and sensory neuronopathies, many of these neuropathies remain refractory to treatment. In select cases, early identification and treatment may result in better outcomes. "Idiopathic" should be a diagnosis of exclusion and a thorough investigation for treatable causes pursued.

Neurological manifestations of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune connective tissue disease affecting the exocrine glands, leading to damage of their structure and impairment of their function. In the course of pSS the internal organs may be involved and the symptoms may concern any system. Neurological disorders are one of the most common extraglandular manifestations of pSS. Available literature data estimate the prevalence of neurological symptoms as about 8.5-70% of patients diagnosed with pSS. The most common neurological complication of pSS is peripheral neuropathy, and in particular sensory polyneuropathy. Central nervous system involvement is much less common. There are also reports of various symptoms connected with damage to cranial nerves and the autonomic nervous system. A careful neurological evaluation, combined with neurophysiological tests, is recommended in patients with pSS. This review summarizes the neurological manifestations of pSS, their possible pathogenic mechanisms, diagnostic evaluation and potential treatment.

Advances in the diagnosis, immunopathogenesis and therapies of IgM-anti-MAG antibody-mediated neuropathies

Polyneuropathy with immunoglobulin M (IgM) monoclonal gammopathy is the most common paraproteinemic neuropathy, comprising a clinicopathologically and immunologically distinct entity. The clinical spectrum spans from distal paresthesias and mild gait imbalance to more severe sensory ataxia, with falls and a varying degree of distal sensorimotor deficits. In approximately 75% of patients, the monoclonal IgM immunoreacts with myelin-associated glycoprotein (MAG) and sulfoglucuronyl glycosphingolipid (SGPG), or other peripheral nerve glycolipids that serve as antigens. These antibodies are considered pathogenic because IgM and complement are deposited on the myelin sheath, splitting the myelin lamellae, while adoptive transfer of patients’ IgM into susceptible host animals causes sensory ataxia and reproduces the human pathology. In spite of the apparently convincing pathogenicity of these antibodies, the response to immunotherapies remains suboptimal. Clorambuscil, cladibrine, cyclophospamide and intravenous immunoglobulin may help some patients but the benefits are minimal and transient. Open-label studies in >200 patients indicate that rituximab is helpful in 30–50% of these patients, even with long-term benefits, probably by suppressing IgM anti-MAG antibodies or inducing immunoregulatory T cells. Two controlled studies with rituximab did not however meet the primary endpoint, mostly because of the poor sensitivity of the scales used; they did however show statistical improvement in secondary endpoints and improved clinical functions in several patients. This review provides an overview of the clinical phenotypes and immunoreactivity of IgM to glycolipids or glycoproteins of peripheral nerve myelin, summarizes the progress on treatment with rituximab as a promising therapy, discusses the pitfalls of scales used, identifies possible biomarkers of response to therapy and highlights the promising new anti-B cell or target-specific immunotherapies.

Sensory Neuronopathies

PURPOSE OF REVIEW

The sensory neuronopathies are sensory-predominant polyneuropathies that result from damage to the dorsal root and trigeminal sensory ganglia. This review explores the various causes of acquired sensory neuronopathies, the approach to diagnosis, and treatment.

RECENT FINDINGS

Diagnostic criteria have recently been published and validated to allow differentiation of sensory neuronopathies from other polyneuropathies. On the basis of serial electrodiagnostic studies, the treatment window for the acquired sensory neuronopathies has been identified as approximately 8 months. If treatment is initiated within 2 months of symptom onset, there is a better opportunity for improvement of the patient's condition. Even though sensory neuronopathies are rare, significant progress has been made regarding characterization of their clinical, electrophysiologic, and imaging features. This does not hold true, however, for treatment. There have been no randomized controlled clinical trials to guide management of these diseases, and a standard treatment approach remains undetermined.

A randomized exploratory phase 2 study in patients with chemotherapy-related peripheral neuropathy evaluating whole-body vibration training as adjunct to an integrated program including massage, passive mobilization and physical exercises

BACKGROUND

Chemotherapy-induced polyneuropathy (CIPN) is a common toxicity after chemotherapy, immunomodulatory drugs or proteasome inhibitors, which is difficult to treat and may also have impact on quality of life. The objective of the study was to evaluate whole-body vibration (WBV) on the background of an integrated program (IP) including massage, passive mobilization and physical exercises on CIPN.

PATIENTS AND METHODS

In an exploratory phase-2 study patients with CIPN (NCI CTC grade 2/3) were randomized for WBV plus IP (experimental) to IP alone (standard). 15 training sessions within 15 weeks were intended. As primary endpoint we used chair-rising test (CRT) to assess physical fitness and coordination. In addition, locomotor and neurological tests and self-assessment tools were performed.

RESULTS

A total 131 patients with CIPN were randomized (standard, n = 65; experimental, n = 66). The median age was 60 (range 24-71) years; 44 patients had haematological neoplasms and 87 solid tumors. At baseline, all patients presented with an abnormal CRT. Fifteen (standard) and 22 (experimental) patients left the program due to progression/relapse or concomitant disease. There was no significant difference in the proportion of patients with normal CRT (<10 s) at follow up between experimental (68%) and standard (56%) (p = 0.20). All patients experienced less symptoms and pain (p < 0.001) and had improved CRT (p < 0.001) over time. WBV was significantly associated with a higher reduction of time needed for CRT (p = 0.02) and significantly improved warm-detection-threshold comparing baseline to follow-up assessment (p = 0.02).

CONCLUSION

Whole-body vibration on the background of an IP may improve physical fitness and coordination in patients suffering from CIPN. Trial registration Retrospectively registered at http://www.iscrtn.com (ISRCTN 51361937) and http://www.clinicaltrials.gov (NCT02846844).

Physiologic Studies of Dysmetria in Patients with Cerebellar Deficits

A feature of cerebellar ataxia is dysmetria, which is characterized by inaccurate movements. Studies of rapid movements at a single joint show prolonged acceleration phases and prolonged initial bursts of EMG activity in the agonist muscle. These two features correlate with each other, suggesting that the prolongation of the neural signal is responsible for the kinematic abnormality. This explains a tendency to hypermetria. Studies of multijoint movements show abnormalities in relative timing of the different joints. During locomotion, knee and ankle motions can be delayed differentially with respect to the gait cycle. Subjects attempting straight-line movements with the arm have systematic deviations that reflect incoordination of the shoulder and elbow with respect to each other. A possible explanation of dysmetria is a failure of sufficient force generation within the necessary time to accomplish a coordinated movement. Another possible explanation is that the cerebellum is responsible for timing of brain functions.

The Distinctive Clinical Features of Paraneoplastic Sensory Neuronopathy

A 15-year experience with paraneoplastic sensory neuronopathy at the Mayo Clinic is reviewed. Of 26 patients with paraneoplastic sensory neuronopathy, 19 had small cell lung cancer, 4 had breast cancer, and 3 had other neoplasms. There was a striking predominance of females (20:6). Neuropathic symptoms (pain, paresthesia, sensory loss) were asymmetric at onset, with a predilection for the upper limbs; in three patients, symptoms were confined to the arms. Electrophysiologic testing revealed absent sensory responses and normal or minimally altered motor responses. Slightly more than half the patients had associated autonomic, cerebellar, or cerebral abnormalities. In some patients, treatment of the neoplasm seemed to halt progression of the neuronopathy, but none had neurologic improvement and most continued to worsen, even when the oncologic response was good. Distinguishing between paraneoplastic and nonparaneoplastic sensory neuronopathies can be difficult, but prominent neuropathic pain, neurologic dysfunction involving more than the peripheral sensory system, or an increased cerebrospinal fluid protein value should prompt a careful search for a cancer.

Egr3-dependent muscle spindle stretch receptor intrafusal muscle fiber differentiation and fusimotor innervation homeostasis

Muscle stretch proprioceptors (muscle spindles) are required for stretch reflexes and locomotor control. Proprioception abnormalities are observed in many human neuropathies, but the mechanisms involved in establishing and maintaining muscle spindle innervation and function are still poorly understood. During skeletal muscle development, sensory (Ia-afferent) innervation induces contacted myotubes to transform into intrafusal muscle fibers that form the stretch receptor core. The transcriptional regulator Egr3 is induced in Ia-afferent contacted myotubes by Neuregulin1 (Nrg1)/ErbB receptor signaling and it has an essential role in spindle morphogenesis and function. Because Egr3 is widely expressed during development and has a pleiotropic function, whether Egr3 functions primarily in skeletal muscle, Ia-afferent neurons, or in Schwann cells that myelinate Ia-afferent axons remains unresolved. In the present studies, cell-specific ablation of Egr3 in mice showed that it has a skeletal muscle autonomous function in stretch receptor development. Moreover, using genetic tracing, we found that Ia-afferent contacted Egr3-deficient myotubes were induced in normal numbers, but their development was blocked to generate one to two shortened fibers that failed to express some characteristic myosin heavy chain (MyHC) proteins. These "spindle remnants" persisted into adulthood, remained innervated by Ia-afferents, and expressed neurotrophin3 (NT3), which is required for Ia-afferent neuron survival. However, they were not innervated by fusimotor axons and they did not express glial derived neurotrophic factor (GDNF), which is essential for fusimotor neuron survival. These results demonstrate that Egr3 has an essential role in regulating gene expression that promotes normal intrafusal muscle fiber differentiation and fusimotor innervation homeostasis.

Clinical assessment of the sensory ataxias; diagnostic algorithm with illustrative cases

Ataxia is a common neurological syndrome resulting from cerebellar, vestibular or sensory disorders. The recognition and characterisation of sensory ataxia remains a challenge. Cerebellar ataxia is the more common and easier to identify; sensory ataxia is often mistaken for cerebellar ataxia, leading to diagnostic errors and delays. A coherent aetiological work-up is only possible if clinicians initially recognise sensory ataxia. We discuss ways to separate sensory from cerebellar ataxia, the causes of sensory ataxia and the clinico-neurophysiological syndromes causing the sensory ataxia syndromes. We summarise a logical tiered approach as a diagnostic algorithm.

Proximally evoked soleus H-reflex to S1 nerve root stimulation in sensory neuronopathies (ganglionopathies)

INTRODUCTION

Sensory neuronopathy (SNN) mimics distal sensory axonopathy. The conventional H-reflex elicited by tibial nerve stimulation (tibial H-reflex) is usually abnormal in both conditions. We evaluated the proximally evoked soleus H-reflex in response to S1 nerve root stimulation (S1 foramen H-reflex) in SNN.

METHODS

Eleven patients with SNN and 6 with distal sensory axonopathy were studied. Tibial and S1 foramen H-reflexes were performed bilaterally in each patient.

RESULTS

Tibial and S1 foramen H-reflexes were absent bilaterally in all patients with SNN. In the patients with distal sensory axonopathy, tibial H-reflexes were absent in 4 and demonstrated prolonged latencies in 2, but S1 foramen H-reflexes were normal.

CONCLUSIONS

Characteristic absence of the H-reflex after both proximal and distal stimulation reflects primary loss of dorsal root ganglion (DRG) neurons and the distinct non-length-dependent impairment of sensory nerve fibers in SNN.

The cutaneous nerve biopsy: technical aspects, indications, and contribution

Skin biopsy with a 3mm disposable circular punch is easy to perform and allows, after proper processing, the visualization of epidermal, dermal, and sweat gland nerve fibers. A technique of sampling the epidermis alone by applying a suction capsule, the "blister" technique, has also been developed. It is most common to stain immunohistochemically for the pan-axonal marker protein gene product 9.5 (PGP 9.5), an ubiquitin C-terminal hydroxylase. The sections are then observed and analyzed with bright-field microscopy or with indirect immunofluorescence with or without confocal microscopy. Most studies report quantification of intraepidermal nerve fiber density displayed in bright-field microscopy. Normative values have been established, particularly from the distal part of the leg, 10cm above the external malleolus. In diabetes mellitus early degeneration of intraepidermal nerve fibers is induced and there is slower regeneration even when there is no evidence of neuropathy. Skin biopsy is of particular value in the diagnosis of small fiber neuropathy when nerve conduction studies are normal. It may also be repeated in order to study the progressive nature of the disease and also has the potential of studying regeneration of nerve fibers and thus the effects of treatment. Inflammatory demyelinating neuropathies may also involve loss of small-diameter nerve fibers and IgM deposits in dermal myelinated nerve fibers in anti-MAG neuropathy. In some cases the presence of vasculitis in skin may indicate a nonsystemic vasculitic neuropathy and in HIV neuropathy intraepidermal nerve fiber density is reduced in a length-dependent manner. In several hereditary neuropathies intraepidermal nerve fiber density may be reduced but other abnormalities can also be demonstrated in dermal myelinated fibers. Some small swellings and varicosities may be present in the distal leg skin biopsy of healthy individuals but large axonal swellings are considered as evidence of a pathological process affecting the normal structure of nerves. The indirect immunofluorescence technique with confocal microscopy provides the opportunity to study the complex structure of sensory receptors and cutaneous myelinated fibers and the innervation of sweat glands, arrector pilorum muscles, and vessels.

Doxorubicin-conjugated PEGylated dendrimers show similar tumoricidal activity but lower systemic toxicity when compared to PEGylated liposome and solution formulations in mouse and rat tumor models

PEGylated polylysine dendrimers show promise as novel drug delivery systems with the potential to direct site specific deposition patterns and to reduce toxicity at nontarget sites. Here the activity and toxicity profiles of a generation 5 polylysine dendrimer with 50% surface conjugation of PEG1100 and 50% surface conjugation of doxorubicin (via an acid labile 4-hydrazinosulfonyl benzoic acid linker) have been compared in a Walker 256 rat tumor model and a human MDA-MB231 xenograft in mice. A direct comparison was also made to a PEGylated liposomal formulation of doxorubicin and a doxorubicin solution. In both rat and mouse breast cancer models, the dendrimer formulation gave equivalent antitumor efficacy when compared to the liposomal or solution doxorubicin formulations and administration of all three doxorubicin formulations resulted in a significant reduction (>75%) in tumor growth in both models at doses ranging from 2 to 10 mg/kg doxorubicin equivalents. The dendrimer formulation, however, was better tolerated by both rats and mice, and approximately 2-fold higher doses were required to induce similar levels of toxicity (as assessed by organ weight, peripheral white cell counts, body weight and survival curves) when compared to administration of the doxorubicin solution or PEGylated liposomal doxorubicin. In rats the appearance of palmar plantar erythematosis (PPE), or hand foot syndrome, was also less evident after administration of dendrimer doxorubicin when compared to the liposome. Finally, even after administration to mice at 2-fold higher doses, dendrimer-doxorubicin resulted in a reduced incidence of cardiotoxicity when compared with a simple solution formulation of doxorubicin. The data suggest that dendrimer-based doxorubicin formulations may provide advantage over solution and liposomal formulations of doxorubicin via a reduction in systemic toxicity.

Sensory neuronopathy and autoimmune diseases

Sensory neuronopathies (SNs) are a specific subgroup of peripheral nervous system diseases characterized by primary degeneration of dorsal root ganglia and their projections. Multifocal sensory symptoms often associated to ataxia are the classical features of SN. Several different etiologies have been described for SNs, but immune-mediated damage plays a key role in most cases. SN may herald the onset of some systemic autoimmune diseases, which further emphasizes how important the recognition of SN is in clinical practice. We have thus reviewed available clinical, neurophysiological, and therapeutic data on autoimmune disease-related SN, namely, in patients with Sjögren's syndrome, autoimmune hepatitis, and celiac disease.

Ataxic sensory neuronopathy in a patient with systemic lupus erythematosus

The occurrence of ataxic sensory neuronopathy (ASN) is rare in patients with connective tissue diseases (CTDs). ASN has been described in case reports and case series in patients with CTDs, mostly Sjögren's syndrome, and most often occurring during middle or old age. ASN in association with systemic lupus erythematosus (SLE) is extremely rare; there has been only one reported case in the literature. In addition, to our knowledge, adolescent onset of symptoms in CTD-associated ASN has not been reported previously. We report the case of a young woman who presented with ASN, characterized by sensory ataxia, with elevated antinuclear antibodies, leukopenia and anemia; she fulfilled the diagnostic criteria for SLE about 7 years after the onset of sensory ataxia. Our case points out that ASN may be the initial presenting feature of SLE. SLE should be included in the differential diagnosis of ASN, especially in patients of young age.

Practical considerations on the use of rituximab in autoimmune neurological disorders

Rituximab (Mabthera, Rituxan) is a chimeric human/murine monoclonal antibody against CD-20 surface antigen expressed on B-cells. Rituximab, by causing B-cell depletion, appears to be effective in several autoimmune disorders; it has been approved for rheumatoid arthritis and is a promising new agent in the treatment of several autoimmune neurological disorders. A controlled study in patients with relapsing remitting multiple sclerosis has shown that rituximab significantly reduces the number of new MRI lesions and improves clinical outcome; it also showed some promise in a subset of patients with primary progressive MS. The drug is also effective in a number of patients with Devic's disease, myasthenia gravis, autoimmune neuropathies, and inflammatory myopathies. The apparent effectiveness of rituximab has moved B-cells into the center stage of clinical and laboratory investigation of autoimmune neurological disorders. We review the evidence-based effectiveness of rituximab in neurological disorders based on controlled trials and anecdotal reports, including our own experience, and address the immunobiology of B-cells in autoimmune central nervous system (CNS) and peripheral nervous system (PNS) disorders. In addition, we provide practical guidelines on how best to use this drug in clinical practice and highlight its potential toxicity.

Isolated degeneration of the posterior column as a distinct entity--a clinical and electrophysiologic follow-up study

OBJECTIVE

The aim of the study was to better describe the long term clinical course and electrophysiologic and radiologic findings in isolated degeneration of the posterior column.

METHODS

Four patients with the presenting symptoms of a progressive tabetic ataxia were followed up clinically and electrophysiologically over up to 15 years between 1997 and 2008. They received standardized neurological examinations, electrophysiologic testing with SEP, MEP, NCV, EMG, autonomic testing and cardiac evaluation, head and spine MRI, laboratory evaluation including CSF analysis.

RESULTS

Progressive gait ataxia due to pallhypasthesia and loss of position sense with areflexia remained the only symptoms. Pes cavus deformity was a notable clinical feature in all cases. There was no involvement of other systems and all patients remained fully ambulatory. There was no cardiac involvement. Electrophysiology was characterized by absent cortical tibial SEP with normal lumbar complexes and normal nerve conduction studies and transcortical magnetic stimulation as well as sympathetic skin response. MRI of the cord was normal. Laboratory analysis and CSF were unrevealing.

CONCLUSION

Isolated degeneration of the posterior column is a rare condition with a clinically benign course without progression involving other systems and characteristic electrophysiologic findings (isolated loss of cortical tibial-SEP with normal lumbar leads). Pes cavus deformity seems to be an unusual but typical clinical feature. The etiology is most likely a sporadic degenerative disease of the cord.

Locomotor adaptation and aftereffects in patients with reduced somatosensory input due to peripheral neuropathy

We studied 12 peripheral neuropathy patients (PNP) and 13 age-matched controls with the "broken escalator" paradigm to see how somatosensory loss affects gait adaptation and the release and recovery ("braking") of the forward trunk overshoot observed during this locomotor aftereffect. Trunk displacement, foot contact signals, and leg electromyograms (EMGs) were recorded while subjects walked onto a stationary sled (BEFORE trials), onto the moving sled (MOVING or adaptation trials), and again onto the stationary sled (AFTER trials). PNP were unsteady during the MOVING trials, but this progressively improved, indicating some adaptation. During the after trials, 77% of control subjects displayed a trunk overshoot aftereffect but over half of the PNP (58%) did not. The PNP without a trunk aftereffect adapted to the MOVING trials by increasing distance traveled; subsequently this was expressed as increased distance traveled during the aftereffect rather than as a trunk overshoot. This clear separation in consequent aftereffects was not seen in the normal controls suggesting that, as a result of somatosensory loss, some PNP use distinctive strategies to negotiate the moving sled, in turn resulting in a distinct aftereffects. In addition, PNP displayed earlier than normal anticipatory leg EMG activity during the first after trial. Although proprioceptive inputs are not critical for the emergence or termination of the aftereffect, somatosensory loss induces profound changes in motor adaptation and anticipation. Our study has found individual differences in adaptive motor performance, indicative that PNP adopt different feed-forward gait compensatory strategies in response to peripheral sensory loss.

The pattern and diagnostic criteria of sensory neuronopathy: a case-control study

Acquired sensory neuronopathies encompass a group of paraneoplastic, dysimmune, toxic or idiopathic disorders characterized by degeneration of peripheral sensory neurons in dorsal root ganglia. As dorsal root ganglia cannot easily be explored, the clinical diagnosis of these disorders may be difficult. The question as to whether there exists a common clinical pattern of sensory neuronopathies, allowing the establishment of validated and easy-to-use diagnostic criteria, has not yet been addressed. In this study, logistic regression was used to construct diagnostic criteria on a retrospective study population of 78 patients with sensory neuronopathies and 56 with other sensory neuropathies. For this, sensory neuronopathy was provisionally considered as unambiguous in 44 patients with paraneoplastic disorder or cisplatin treatment and likely in 34 with a dysimmune or idiopathic setting who may theoretically have another form of neuropathy. To test the homogeneity of the sensory neuronopathy population, likely candidates were compared with unambiguous cases and then the whole population was compared with the other sensory neuropathies population. Criteria accuracy was checked on 37 prospective patients referred for diagnosis of sensory neuropathy. In the study population, sensory neuronopathy showed a common clinical and electrophysiological pattern that was independent of the underlying cause, including unusual forms with only patchy sensory loss, mild electrical motor nerve abnormalities and predominant small fibre or isolated lower limb involvement. Logistic regression allowed the construction of a set of criteria that gave fair results with the following combination: ataxia in the lower or upper limbs + asymmetrical distribution + sensory loss not restricted to the lower limbs + at least one sensory action potential absent or three sensory action potentials <30% of the lower limit of normal in the upper limbs + less than two nerves with abnormal motor nerve conduction study in the lower limbs.

Dorsal root ganglionectomy for the diagnosis of sensory neuropathies. Surgical technique and results

BACKGROUND

Inflammatory diseases stand out among sensory neuronopathies because, in their active phase, they can be treated with immunosuppressive agents. Immunosuppressive therapy may present severe adverse effects and requires previous inflammatory activity confirmation. Sensory neuronopathies are diagnosed based on clinical and EMG findings. Diagnostic confirmation and identification of inflammatory activity are based on sensory ganglion histopathological examination. We describe the surgical technique used for dorsal root ganglionectomy in patients with clinical/EMG diagnosis of sensory neuronopathies.

METHODS

The sensory ganglion was obtained from 15 patients through a small T7-T8 hemilaminectomy and foraminotomy to expose the C7 root from its origin to the spinal nerve bifurcation. In 6 patients, the dural cuff supposed to contain the ganglion was resected en bloc; and in 9 patients, the ganglion was obtained through a longitudinal incision of the dural cuff and microsurgical dissection from the ventral and dorsal roots and radicular arteries. All ganglia were histopathologically examined.

RESULTS

No ganglion was found in the dural cuff in 2 patients submitted to en bloc removal, and the ganglion was removed in all patients who underwent microsurgical dissection. All but 2 patients that had ganglion examination presented a neuronopathy of nerve cell loss, 3 with mononuclear inflammatory infiltrate. These patients underwent immunosuppressive therapy, and 2 of them presented clinical improvement. No surgical complications were observed.

CONCLUSIONS

Microsurgical dorsal root ganglionectomy for diagnosing inflammatory sensory ganglionopathies was effective and safe. Although safe, en bloc resection of the proximal dural cuff was not effective for this purpose.

Acute sensory neuronopathy as the presenting symptom of Sjögren’s syndrome

Sensory neuronopathy associated with Sjögren's syndrome (SS) usually has a subacute or chronic onset. We report the case of a 37-year-old woman who presented with an unusual hyperacute form of SS ganglionopathy. She initially developed paresthesias of her fingertips and rapidly became severely ataxic. Nerve conduction studies revealed abnormal sensory but normal motor functions. Lip biopsy showed findings consistent with SS. Sural nerve biopsy showed severe axonal loss. The patient showed modest improvement with immunosuppressive therapies.

Sensory neuron diseases

Sensory neuron diseases (SND) are a distinct subgroup of peripheral-nervous-system diseases, first acknowledged in 1948. Acquired SND have a subacute or chronic course and are associated with systemic immune-mediated diseases, vitamin intoxication or deficiency, neurotoxic drugs, and life-threatening diseases such as cancer. SND are commonly idiopathic but can be genetic diseases; the latter tend to involve subtypes of sensory neurons and are associated with certain clinical pictures. The loss of sensory neurons in dorsal root ganglia causes the degeneration of short and long peripheral axons and central sensory projections in the posterior columns. This pathological process leads to a pattern of sensory nerve degeneration that is not length dependent and explains distinct clinical and neurophysiological abnormalities. Here we propose a comprehensive approach to the diagnosis of acquired and hereditary SND and discuss clinical, genetic, neurophysiological, neuroradiological, and neuropathological assessments.

[The diagnosis of acquired sensory neuropathies]

INTRODUCTION

Peripheral neuropathies usually include a sensory component of various causes. The diagnosis approach requires careful a clinical assessment and a precise electrophysiological exploration.

STATE OF ART

Axonal sensory polyneuropathies are classified according to the type of fibers involved (large or small fibers). While there is a large number of causes, current emphasis is placed on glucose intolerance as a source of small-fiber sensory neuropathies. Demyelinating polyneuropathies are often associated with a monoclonal IgM gammapathy with anti-MAG activity. Multiple sensory mononeuropathies are exceptional and suggest possible early-phase vasculities, sensorymotor neuropathy with conduction blocks or leprosy. Sensory neuronopathies can also suggest Sjögren's syndrome or a paraneoplastic syndrome. Finally chronic sensory polyradiculoneuritis constitute a rare subgroup clearly defined as demyelinating inflammatory neuropathy.

CONCLUSION

The diagnostic approach to sensory neuropathies requires careful nosological electroclinical classification to reduce the number of explorations performed for etiological diagnosis.

Antibodies to dorsal root ganglia and olfactory cells in a patient with chronic sensory neuropathy and anosmia

We report the case of a 51-year-old woman with anosmia and chronic sensory ataxic neuropathy. Olfactory tests suggested neurosensory anosmia. Immunocytochemical analysis showed serum antibodies against dorsal root ganglion (DRG) cells and olfactory neurons, in the absence of other known causes of anosmia and sensory neuropathy. Clinical and laboratory data suggested a slow autoimmune process affecting dorsal root ganglion and olfactory cells.

Epidermal nerve fiber density in sensory ganglionopathies: clinical and neurophysiologic correlations

We assessed the involvement of somatic unmyelinated fibers in sensory ganglionopathies by skin biopsy and quantitative sensory testing (QST). Sixteen patients with ganglionopathy, 16 with axonal neuropathy, and 15 normal controls underwent skin biopsy at the proximal thigh and the distal leg. Intraepidermal nerve fibers (IENF) were immunostained by antiprotein gene product 9.5, and their linear density was quantified under light microscopy. Confocal microscopy studies with double staining of nerve fibers and basement membrane were also performed. Healthy subjects and neuropathy patients showed the typical proximodistal gradient of IENF density; in neuropathies, values were significantly lower at the distal site of the leg, confirming the length-dependent loss of cutaneous innervation. Conversely, ganglionopathy patients with hyperalgesic symptoms did not show any change of IENF density between the proximal thigh and the distal leg. The distinct pattern of epidermal denervation seen in sensory ganglionopathy reflected the degeneration of somatic unmyelinated fibers in a fashion that was not length-dependent, which was consistent with both clinical and neurophysiologic observations and supported the diagnosis.

Retrospective cohort study of 148 patients with polyclonal gammopathy

OBJECTIVE

To quantify clinical conditions and laboratory values associated with moderate to marked polyclonal gammopathy.

PATIENTS AND METHODS

Patient characteristics, laboratory correlates, evolving disease states, and survival of all patients seen at the Mayo Clinic, Rochester, Minn, during 1991 with a polyclonal gamma globulin level of 3.0 g/dL or higher were reviewed in this retrospective cohort study.

RESULTS

One hundred forty-eight patients were identified (median age, 58 years; 59% female). In 130 patients (88%), only 1 diagnosis was identified. Liver disease was the most common single disease association in 79 (61%) of 130 patients, followed by connective tissue diseases in 28 (22%), chronic infections in 8 (6%), hematologic disorders in 6 (5%), and nonhematologic malignancies in 4 (3%). No difference in gamma globulin levels existed between groups. With a median follow-up of 67 months, 90 (63%) of 143 patients for whom follow-up was available were alive. By multivariate analysis, age, albumin concentration, disease group, and platelet count were predictive of survival. No patient developed myeloma or a clonal plasmaproliferative disorder.

CONCLUSION

Moderate to marked polyclonal gammopathy may reflect an underlying condition: liver disease, connective tissue disease, hematologic disorder, infection, or malignancy.

Ataxic form of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)

We reported a 64-year-old male with an eight-month history of gait disturbance and sensory impairment. The patient initially noticed unsteadiness of gait and numbness in his feet, and these symptoms progressed until he was unable to walk without assistance five months later. Vibratory sensation and position sense were markedly diminished, and deep tendon reflexes were absent in all extremities. Motor conduction velocities were slow with prolonged distal latencies, and sensory nerve action potentials (SNAP) were not elicited. Sural nerve biopsy revealed a mild loss of myelinated fibres and segmental demyelination. Cerebrospinal fluid showed normal cell count with protein 526 mg/dL. Anti-GM1, anti-GM2 and anti-GA1 antibodies in serum were positive. We diagnosed chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) presenting ataxia. Steroid therapy provided immediate improvement of symptoms and signs. This case suggests that CIDP should be considered as one of the potential causes of ataxic neuropathy.

Movement-related cerebellar activation in the absence of sensory input

Movement-related cerebellar activation may be due to sensory or motor processing. Ordinarily, sensory and motor processing are obligatorily linked, but in patients who have severe pansensory neuropathies with normal muscle strength, motor activity occurs in isolation. In the present study, positron emission tomography and functional magnetic resonance imaging in such patients showed no cerebellar activation with passive movement, whereas there was prominent movement-related cerebellar activation despite absence of proprioceptive or visual input. The results indicate that motor processing occurs within the cerebellum and do not support the recently advanced view that the cerebellum is primarily a sensory organ.

Proprioceptive control of posture: a review of new concepts

The assumption that proprioceptive inputs from the lower legs are used to trigger balance and gait movements is questioned in this review (an outgrowth of discussions initiated during the Neural Control of Movement Satellite meeting held in Cozumel, Mexico, April 1997). Recent findings presented here suggest that trunk or hip inputs may be more important in triggering human balance corrections and that proprioceptive input from the lower legs mainly helps with the final shaping and intermuscular coordination of postural and gait movements. Three major questions were considered. First, what role, if any, do lower-leg proprioceptive inputs play in the triggering of normal balance corrections? If this role is negligible, which alternative proprioceptive inputs then trigger balance corrections? Second, what is the effect of proprioceptive loss on the triggering of postural and gait movements? Third, how does proprioceptive loss affect the output of central pattern generators in providing the final shaping of postural movements? The authors conclude that postural and gait movements are centrally organized at two levels. The first level involves the generation of the basic directional-specific response pattern based primarily on hip or trunk proprioceptive input secondarily on vestibular inputs. This pattern specifies the spatial characteristics of muscle activation, that is which muscles are primarily activated, as well as intermuscular timing, that is, the sequence in which muscles are activated. The second level is involved in the shaping of centrally set activation patterns on the basis of multisensorial afferent input (including proprioceptive input from all body segments and vestibular sensors) in order that movements can adapt to different task conditions. Copyright 1998 Elsevier Science B.V.