The Distinctive Clinical Features of Paraneoplastic Sensory Neuronopathy

Diagnosis and Treatment of Paraneoplastic Neurologic Syndromes

Paraneoplastic antibody syndromes result from the anti-tumor antibody response against normal antigens ectopically expressed by tumor cells. Although this antibody response plays an important role in helping clear a nascent or established tumor, the engagement of antigens expressed in healthy tissues can lead to complex clinical syndromes with challenging diagnosis and management. The majority of known paraneoplastic antibody syndromes have been found to affect the central and peripheral nervous system. The present review provides an update on the pathophysiology of paraneoplastic neurologic syndromes, as well as recommendations for their diagnosis and treatment.

Paraneoplastic Neurologic Disorders

PURPOSE OF REVIEW

To provide an overview and highlight recent updates in the field of paraneoplastic neurologic disorders.

RECENT FINDINGS

The prevalence of paraneoplastic neurologic disorders is greater than previously reported and the incidence has been rising over time, due to improved recognition in the era of antibody biomarkers. Updated diagnostic criteria that are broadly inclusive and also contain diagnostic risk for clinical presentations (high and intermediate) and diagnostic antibodies (high, intermediate, and low) have replaced the original 2004 criteria. Antibody biomarkers continue to be characterized (e.g., KLHL-11 associated with seminoma in men with brainstem encephalitis). Some paraneoplastic antibodies also provide insight into likely immunotherapy response and prognosis. The rise of immune checkpoint inhibitors as cancer therapeutics has been associated with newly observed immune-mediated adverse effects including paraneoplastic neurological disorders. The therapeutic approach to paraneoplastic neurologic disorders is centered around cancer care and trials of immune therapy. The field of paraneoplastic neurologic disorders continues to be advanced by the identification of novel antibody biomarkers which have diagnostic utility, and give insight into likely treatment responses and outcomes.

Association between chronic inflammatory demyelinating polyneuropathy and gastrointestinal malignancies

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an uncommon and under-recognized immune-mediated disorder of the peripheral nervous system. It is associated with both infectious and non-infectious etiologies and presents in several variant forms. In rare instances, CIDP has been reported in association with gastrointestinal (esophageal, hepatic, colorectal, and pancreatic) malignancies. The diagnosis of malignancy is typically preceded by weeks to months by that of CIDP, though the inverse may also be seen. As with other etiologies of CIDP, cases associated with gastrointestinal malignancies are often treated with corticosteroids, intravenous immunoglobulins, and/or plasma exchange, with improvement or resolution of neurological symptoms in the majority of cases. In this review, we provide a practical overview of CIDP, with an emphasis on recognizing the clinical association between CIDP and gastrointestinal malignancies.

Paraneoplastic Diseases of the Central Nervous System

Paraneoplastic neurological syndromes are nonmetastatic complications of malignancy secondary to immune-mediated neuronal dysfunction or death. Pathogenesis may occur from cell surface binding of antineuronal antibodies leading to dysfunction of the target protein, or from antibodies binding against intracellular antigens which ultimately leads to cell death. There are several classical neurological paraneoplastic phenotypes including subacute cerebellar degeneration, limbic encephalitis, encephalomyelitis, and dorsal sensory neuropathy. The patient’s clinical presentations may be suggestive to the treating clinician as to the specific underlying paraneoplastic antibody. Specific antibodies often correlate with the specific underlying tumor type, and malignancy screening is essential in all patients with paraneoplastic neurological disease. Prompt initiation of immunotherapy is essential in the treatment of patients with paraneoplastic neurological disease, often more effective in cell surface antibodies in comparison to intracellular antibodies, as is removal of the underlying tumor.

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.

Autoimmune paraneoplastic syndromes associated to lung cancer: A systematic review of the literature Part 4: Neurological paraneoplastic syndromes, involving the peripheral nervous system and the neuromuscular junction and muscles

The development of new immune treatment in oncology and particularly for lung cancer may induce new complications, particularly activation or reactivation of auto-immune diseases. In this context, a systematic review on the auto-immune paraneoplastic syndromes that can complicate lung cancer appears useful. This article is the fourth of a series of five and deals mainly with neurological paraneoplastic syndromes involving the peripheral nervous system and the neuromuscular junction and muscles.

Paraneoplastic neuropathy

Recent progress in serological screening of paraneoplastic antibodies and in diagnostic imaging techniques to detect malignancies has enabled a broadening of the concept of paraneoplastic neurological syndromes by integrating nonclassic clinical features. The peripheral nervous system is frequently involved in patients with paraneoplastic syndrome and may be seen alone or in combination with involvement of other areas of the nervous system. Destruction of dorsal root ganglion cells due to lymphocytic infiltration, especially with CD8-positive cytotoxic T cells, has been postulated to mediate the classic syndrome of subacute sensory neuronopathy. However, the motor and autonomic nervous systems are frequently affected. Indeed, patients can develop clinical features compatible with Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, or brachial plexopathy. Other forms of paraneoplastic neuropathy are vasculitic neuropathy, autoimmune autonomic ganglionopathy, and chronic intestinal pseudo-obstruction. Various onconeural antibodies, including anti-Hu, anti-CV2/CRMP-5, and anti-ganglionic acetylcholine receptor antibodies, are associated with neuropathy. Somatic neuropathy is the most common manifestation in patients with anti-Hu and anti-CV2/CRMP-5 antibodies, while anti-ganglionic acetylcholine receptor antibody is associated with autonomic neuropathies. A whole-body fluorodeoxyglucose positron emission tomography scan may be useful to detect malignancy in patients with unremarkable conventional radiological findings. Recognition and diagnosis of paraneoplastic neuropathy is important, as neuropathic symptoms usually precede the identification of the primary tumor, and treatment at an earlier stage provides better chances of good outcomes.

Subclinical peripheral neuropathy is a common finding in colorectal cancer patients prior to chemotherapy

PURPOSE

Of the numerous complications associated with cancer and cancer treatment, peripheral neuropathy is a deleterious and persistent patient complaint commonly attributed to chemotherapy. The present study investigated the occurrence of subclinical peripheral neuropathy in patients with colorectal cancer before the initiation of chemotherapy.

EXPERIMENTAL DESIGN

Fifty-two patients underwent extensive quantitative sensory testing (QST) before receiving chemotherapy. Changes in multiple functions of primary afferent fibers were assessed and compared with a group of healthy control subjects. Skin temperature, sensorimotor function, sharpness detection, and thermal detection were measured, as was touch detection, using both conventional (von Frey monofilaments) and novel (Bumps detection test) methodology.

RESULTS

Patients had subclinical deficits, especially in sensorimotor function, detection of thermal stimuli, and touch detection that were present before the initiation of chemotherapy. The measured impairment in touch sensation was especially pronounced when using the Bumps detection test.

CONCLUSIONS

The patients with colorectal cancer in this study exhibited deficits in sensory function before undergoing chemotherapy treatment, implicating the disease itself as a contributing factor in chemotherapy-induced peripheral neuropathy. The widespread nature of the observed deficits further indicated that cancer is affecting multiple primary afferent subtypes. Specific to the finding of impaired touch sensation, results from this study highlight the use of newly used methodology, the Bumps detection test, as a sensitive and useful tool in the early detection of peripheral neuropathy.

Paraneoplastic motor neuron disease associated with Purkinje cell autoantibody type 1

Motor neuron disease has been reported as a rare result of systemic cancers, likely related to an autoimmune effecter mechanism. These patients have been described as having a more rapid onset of symptoms than typical motor neuron disease. Few of these reports demonstrate an association of a cancer-related autoantibody and with motor neuron disease. We present a 54-year-old woman with infiltrating ductal carcinoma of the breast who later developed lower motor neuron disease and was found to have Purkinje cell autoantibodies type 1. The association of lower motor neuron disease as a consequence of breast cancer with this autoantibody profile has not been described previously. This report emphasizes the importance of considering a paraneoplastic syndrome in a patient with an uncommon presentation of motor neuron disease.

Update on paraneoplastic neurologic disorders

When patients with cancer develop neurologic symptoms, common causes include metastasis, infections, coagulopathy, metabolic or nutritional disturbances, and neurotoxicity from treatments. A thorough clinical history, temporal association with cancer therapies, and results of ancillary tests usually reveal one of these mechanisms as the etiology. When no etiology is identified, the diagnosis considered is often that of a paraneoplastic neurologic disorder (PND). With the recognition that PNDs are more frequent than previously thought, the availability of diagnostic tests, and the fact that, for some PNDs, treatment helps, PNDs should no longer be considered diagnostic zebras, and when appropriate should be included in the differential diagnosis early in the evaluation.

Update on paraneoplastic neurologic disorders

Once considered rare, paraneoplastic neurologic disorders (PNDs) are an extensive group of neurologic disorders that occur either exclusively or at increased frequency in patients with cancer. PNDs have been increasingly recognized due in large part to the identification of antineuronal antibodies in the serum and cerebrospinal fluid of patients. Although almost any neoplasm can cause PND, the tumors most commonly involved are small-cell lung cancer, cancers of the breast and ovary, thymoma, neuroblastoma, plasma cell tumors, and ovarian teratoma. Establishing the diagnosis of PND is important because in more than two-thirds of patients the neurologic symptoms develop before the presence of the cancer is known. When PND is suspected and no tumor is found, it is recommended that cancer screening be repeated every 6 months. Early diagnosis and intervention offers the best chance of neurologic stabilization or improvement.

Achalasia, chronic sensory neuropathy, and N-type calcium channel autoantibodies: beneficial response to IVIG

Autoimmune gastrointestinal dysmotility (AGID) can result from paraneoplastic onconeuronal antibodies. Patients may present with regional hypomotility anywhere along the gastrointestinal tract. We report a case of a woman who developed an insidious sensory neuropathy and achalasia. She was found to have a high-titer of N-type voltage gated-calcium channel (VGCC) antibodies. She demonstrated clinical and electrophysiological improvement of her neuropathy, as well as improvement of her swallowing and gait, after treatment with intravenous immunoglobulins.

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.

Orofacial pain in cancer: part II--clinical perspectives and management

Cancer-associated pain is extremely common and is associated with significant physical and psychological suffering. Unfortunately, pain associated with cancer or its treatment is frequently under-treated, probably due to several factors, including phobia of opioids, under-reporting by patients, and under-diagnosis by healthcare workers. The most common etiology of cancer pain is local tumor invasion (primary or metastatic), involving inflammatory and neuropathic mechanisms; these have been reviewed in Part I. As malignant disease advances, pain usually becomes more frequent and more intense. Additional expressions of orofacial cancer pain include distant tumor effects, involving paraneoplastic mechanisms. Pain secondary to cancer therapy varies with the treatment modalities used: Chemo-radiotherapy protocols are typically associated with painful mucositis and neurotoxicity. Surgical therapies often result in nerve and tissue damage, leading, in the long term, to myofascial and neuropathic pain syndromes. In the present article, we review the clinical presentation of cancer-associated orofacial pain at various stages: initial diagnosis, during therapy (chemo-, radiotherapy, surgery), and in the post-therapy period. As a presenting symptom of orofacial cancer, pain is often of low intensity and diagnostically unreliable. Diagnosis, treatment, and prevention of pain in cancer require knowledge of the presenting characteristics, factors, and mechanisms involved.

Diffuse cranial nerve and cauda equina lesions associated with breast cancer

We report on the case of a patient with breast cancer with diffuse cranial nerve and cauda equina lesions. Magnetic resonance imaging of the patient's brain and spinal cord showed diffuse abnormal enhancement and slight enlargement of the cranial nerves and cauda equina. Although the results of subsequent testing for two antineural antibodies were negative, paraneoplastic sensorimotor neuropathy associated with breast cancer was considered to be the most likely clinical diagnosis.

Adie's pupils in paraneoplastic ganglionopathy with ANNA-1

Autonomic disturbances are common in patients with paraneoplastic syndromes associated with type-1 antineuronal nuclear autoantibodies (ANNA-1), although pupillary disturbances are infrequent. The authors describe a patient with ANNA-1 associated paraneoplastic sensory neuronopathy and bilateral Adie's pupils.

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.

Managing paraneoplastic neurological disorders

Paraneoplastic neurological syndromes (PNS) are remote effects of cancer that are not caused by invasion of the tumor or its metastases. Immunologic factors appear important in the pathogenesis of PNS because antineuronal autoantibodies and T-cell responses against nervous system antigens have been defined for many of these disorders. The immunologic response is elicited by the ectopic expression of neuronal antigens by the tumor. Expression of these so-called "onconeural" antigens is limited to the tumor and the nervous system and sometimes also the testis. At the time of presentation of the neurological symptoms, most patients have not yet been diagnosed with cancer. Detection of paraneoplastic antibodies is extremely helpful in diagnosing an otherwise unexplained and often rapidly progressive neurological syndrome as paraneoplastic. In addition, the paraneoplastic antibodies may also direct the search for an underlying neoplasm. On the other hand, in patients known to have cancer, the presentation of a PNS may herald recurrence of the tumor or a second tumor. The number of paraneoplastic antibodies is still growing, and at least seven of these can now be considered well characterized. Based on the clinical syndrome, the type of antibody, and the presence or absence of cancer, patients are classified as having a "definite" or "possible" PNS. Despite the presumed autoimmune etiology of PNS, the results of various forms of immunotherapy have been disappointing, with some exceptions. Rapid detection and immediate treatment of the underlying tumor appears to offer the best chance of stabilizing the patient and preventing further neurological deterioration.

Lymphoma and peripheral neuropathy: a clinical review

Lymphoma occasionally affects the peripheral nervous system. When it does, the diagnosis can be elusive since many patients present without known lymphoma. Most peripheral nerve complications are due to non-Hodgkin's lymphoma (NHL), which infiltrates nerves causing axonal damage. This disorder can affect nerve roots and cranial nerves, often associated with lymphomatous meningitis. NHL may also infiltrate peripheral nerves and cause plexopathy, mononeuropathy, or generalized neuropathy. These neuropathies may resemble an asymmetric mononeuropathy multiplex or a generalized disorder such as chronic inflammatory demyelinating polyradiculoneuropathy. When NHL infiltrates diffusely, the term neurolymphomatosis is used. Hodgkin's lymphoma (HL), by contrast, rarely infiltrates nerves. More often, HL causes immunological disorders of the peripheral nervous system such as inflammatory plexopathy or Guillain-Barré syndrome. Other rare lymphomas such as intravascular lymphoma and Waldenstrom's macroglobulinemia can also affect peripheral nerves in specific ways. In addition, other malignant and nonmalignant lymphoproliferative disorders enter into the differential diagnosis of lymphomatous neuropathy. This review discusses the multiple peripheral nerve presentations of lymphoma from the clinician's point of view and provides a guide to the evaluation and diagnosis of these uncommon, challenging disorders.

Immunological features of neurological paraneoplastic syndromes

Neurological paraneoplastic syndromes are a rare group of disorders that occur in 1-2% of people with malignancy. They are usually caused by an immune response, triggered by and directed against a tumour, that cross-reacts with protein expressed by the peripheral or central nervous system. Any part of the nervous system can be affected and patients often develop severe and permanent disability. Diagnosis can be difficult as in two-thirds of patients the neurological problems appear up to 5 years before the tumour manifests. However, certain of these syndromes are often associated with specific serum autoantibodies that can be useful both in diagnosis of the neurological syndrome and in focusing the search for a particular tumour. Thus, these antibodies can allow earlier identification and treatment of cancer and, potentially, a reduction in morbidity and mortality. It was only in the 1980s that the first anti-neuronal autoantibodies were characterized and their associations with clinical syndromes and tumours defined. Further antibodies have been isolated over the past 20 years and novel pathogenic mechanisms for several syndromes have been recognized. For example, voltage-gate ion channels seem to be a common target for autoantibodies involved in peripheral nerve diseases such as the Lambert-Eaton myasthenic syndrome and neuromyotonia (Isaacs' syndrome). However, the place of most paraneoplastic antibodies in the pathogenesis of central syndromes is yet to be fully elucidated.

Small fiber neuropathy: a common and important clinical disorder

Small fiber neuropathy (SFN) is a neuropathy selectively involving small diameter myelinated and unmyelinated nerve fibers. Interest in this disorder has considerably increased during the past few years. It is often idiopathic and typically presents with peripheral pain and/or symptoms of autonomic dysfunction. Diagnosis is made on the basis of the clinical features, normal nerve conduction studies (NCS) and abnormal specialized tests of small nerve fibers. Among others, these tests include assessment of epidermal nerve fiber density, temperature sensation tests for sensory fibers and sudomotor and cardiovagal testing (QSART) for autonomic fibers. Unless an underlying disease is identified, treatment is usually symptomatic and directed towards alleviation of neuropathic pain.

Les neuropathies périphériques paranéoplasiques

Paraneoplastic peripheral neuropathies constitute a heterogeneous group of conditions. A link between the tumor and the neuropathy has been demonstrated in a subgroup only. Definite paraneoplastic neuropathies correspond to neuropathies associated with antibodies reacting with antigens common to the peripheral nervous system and the cancer. Neuropathies associated with anti-Hu antibodies are the most frequent and consist mainly in subacute sensory neuronopathy. Sensory or sensory-motor neuropathies with anti-CV2 antibodies are less frequent. The link between the cancer and the neuropathy is less clear in the other forms. The frequency of cancer in this group varies from 1 to 18 p.cent.These neuropathies include inflammatory demyelinating neuropathies, neuropathy and vasculitis, lower motor neurone diseases, and autonomic neuropathies. Occasionally, the neuropathy improves with treatment of the tumor. Recent data suggest that gangliosides may be the target of the immune process in neuropathies associated with melanoma.

Clinical features and pathophysiological basis of sensory neuronopathies (ganglionopathies)

Sensory ganglionopathies have a frequent association with neoplastic disorders (paraneoplastic subacute sensory neuronopathy, or SSN) or dysimmune disorders (Sjögren's syndrome, SS; Miller Fisher syndrome; and Bickerstaff's brainstem encephalitis, BBE), with drugs, such as cisplatin or pyridoxine, and with inherited disorders with degeneration of dorsal root ganglion cells. Unsteady gait and pseudoathetoid movements of the hand are the distinctive signs encountered in these disorders. The chronic disorders are characterized by non-length-dependent abnormalities of sensory nerve action potentials (SNAPs) and differ from other sensory neuropathies in showing a global, rather than distal, decrease in SNAP amplitudes. This review focuses on recent advances in defining the mechanisms involved in sensory ganglionopathies. Specific topics include a summary of their clinical features, pathological findings, and immunopathology. In SSN, early diagnosis by the detection of anti-Hu antibodies and early treatment of the cancer gives the best chance of stabilizing the disorder. In SS sensory ganglionitis, response to treatment has been disappointing, but immunomodulating treatments are emerging. The immunological profile common to BBE and Fisher syndrome supports a common pathogenesis. In toxic sensory neuronopathy, no treatment is available. The differential diagnosis involves separating sensory ganglionopathies from other ataxic polyneuropathies, such as infectious neuropathies, sensory neuropathies with various autoantibodies, and the neuropathies seen in celiac disease.

Spectrum of paraneoplastic neurologic disorders in women with breast and gynecologic cancer

We conducted the current review of the paraneoplastic neurologic syndromes (PNSs) associated with gynecologic and breast carcinomas to describe their clinical and immunologic characteristics and their relative frequency. We retrospectively reviewed 92 patients whose serum was sent to our laboratories to detect onconeural antibodies and who were diagnosed as having PNSs associated with breast or gynecologic tumors. PNSs were defined as "definitive" and "possible" (atypical PNS, no onconeural antibodies, and no improvement after tumor treatment). Forty-nine patients had breast and 43 had gynecologic cancer. Sixty-three patients had onconeural antibodies (50 Yo-ab, 5 Hu-ab, 5 Ri-ab, and 3 amphiphysin-ab). Cerebellar ataxia represented 57 (62%) of all PNSs and was associated with anti-Yo in 88%. All Yo-abnegative patients had breast cancer; 4 of them had a mild cerebellar syndrome that improved after tumor treatment. Sensorypredominant neuropathies were present in 17 (18%) patients. Seven of them had Hu-ab (5) or amphiphysin-ab (2). Other PNSs were opsoclonus-myoclonus syndrome (4 cases, Ri-ab in 2), sensorimotor neuropathy (4 cases), paraneoplastic encephalomyelitis (4 cases, Ri-ab in 3), paraneoplastic retinopathy (2 cases), amyotrophic lateral sclerosis (2 cases), stiff-person syndrome (1 with amphiphysin-ab), and limbic encephalitis (1 case). All patients with gynecologic cancer presented definitive PNS, and onconeural antibodies were diagnosed in 93% of them. In contrast, 20% of PNSs associated with breast cancer were defined as possible and the incidence of onconeural antibodies was 51%, excluding the 2 patients with paraneoplastic retinopathy in whom antiretinal antibodies were not analyzed. In patients with possible PNS, a coincidental association between the tumor and the neurologic disorder cannot be excluded.

Neuromuscular complications of cancer

Neuromuscular complications of cancer are common and can affect any component of the peripheral nervous system from peripheral nerve cell body to muscle. Perhaps the most common complication is a length-dependent symmetric axonal polyneuropathy that is often multifactorial in etiology, resulting from metabolic and treatment effects of the primary malignancy. However, neuromuscular disorders may also be the presenting complaint in many conditions, including disorders caused by malignant infiltration of nerve and disorders cause by paraneoplastic syndromes. Although many of the paraneoplastic conditions are poorly responsive to treatment, not all are, and one hopes that prompt diagnosis of the underlying malignancy will lead to improved patient outcome. Recognition of iatrogenic neuromuscular complications is also important to modify treatment protocols when possible and thus decrease the risk of long-term neurologic disability.

Paraneoplastic neurologic syndromes

Cancer can affect the nervous system through many metastatic and nonmetastatic mechanisms, including side effects of cancer treatment, infections, coagulopathy, and metabolic or nutritional deficits. Paraneoplastic neurologic disorders (PND) are an extensive group of syndromes that cannot be explained by any of these complications and may affect any part of the nervous system. PND often develop before the presence of a cancer is known and their recognition may lead to the tumor diagnosis.

Remote neurologic manifestations of cancer

Paraneoplastic disorders may affect any part of the central or peripheral nervous systems. Although relatively uncommon, these disorders are a significant cause of neurologic morbidity for cancer patients. At least some paraneoplastic syndromes are believed to be caused by an autoimmune reaction against shared tumor-neural antigens. This article summarizes the clinical features of paraneoplastic disorders, the current evidence for autoimmunity, and guidelines for diagnosis and treatment.

The clinical spectrum and pathogenesis of paraneoplastic disorders of the central nervous system

Paraneoplastic neurologic disorders (PND) refer to neurologic disorders of unknown cause that occur at higher frequency in patients with cancer than in the general population. There is increasing evidence that many of these disorders are immune mediated and associated with cytotoxic antitumor immunity. The identification of the immune responses in these patients facilitates the diagnosis of the PND and has led to the cloning and characterization of the target antigens in the nervous system and tumor.

Paraneoplastic syndromes of the spinal cord, nerve, and muscle

Cancer can affect the peripheral nervous system by non-metastatic, sometimes immune-mediated mechanisms. Recognition of these paraneoplastic syndromes is important because it can lead to the detection of the tumor, and also helps to avoid unnecessary studies to determine the cause of the neurologic symptoms in patients with cancer. Many paraneoplastic syndromes of the peripheral nervous system are not associated with serum antibodies that serve as markers of paraneoplasia. For this group of disorders the diagnosis depends on the clinician's index of suspicion and conventional electrophysiologic and laboratory tests. Treatment of the tumor, immunotherapy, or both may improve some of these syndromes. This review focuses on paraneoplastic syndromes of the spinal cord, peripheral nerve, and muscle.

Subacute sensory neuropathy associated with Epstein-Barr virus

A 35-year-old man experienced severe sensory loss, pseudoathetosis, and areflexia during recovery from a severe viral illness. Sensory nerve action potentials were absent, motor conduction velocities were mildly slowed, and blink reflexes were normal. Magnetic resonance imaging (MRI) revealed abnormal signal within the central and dorsal aspects of the thoracic cord. Acute and convalescent Epstein-Barr virus (EBV) titers suggested EBV as the etiology. Subacute sensory neuropathy, with peripheral and central nervous system involvement, is a rare complication of EBV infection.

Paraneoplastic painful ulnar neuropathy

A 58-year-old woman developed painful, bilateral ulnar neuropathy in conjunction with small cell lung carcinoma and high serum titer of anti-Hu antibody. An incidental stage I plasma cell dyscrasia, with immunoglobulin G kappa monoclonal protein, was also present. Electropysiological assessment excluded a generalized neuropathy, and nerve biopsy showed marked loss of myelinated and small unmyelinated fibers, without inflammatory changes or amyloid deposition. High titers of circulating anti-Hu antibody can be associated with symptoms resembling a paraneoplastic mononeuropathy.

Neurologic paraneoplastic syndromes

Several neurologic paraneoplastic disorders are believed to be caused by an autoimmune reaction against antigen(s) co-expressed by tumour cells and neurons. Of the paraneoplastic syndromes, the evidence for an autoimmune etiology is strongest for the Lambert-Eaton myasthenic syndrome, in which autoantibodies downregulate voltage-gated calcium channels at the presynaptic nerve terminal. For other syndromes, including cerebellar degeneration, multifocal encephalomyelitis, sensory neuronopathy, limbic encephalitis, opsoclonus-myoclonus, stiff person syndrome, and retinal degeneration, the autoimmune theory is supported by the presence of specific antineuronal antibodies. These antibodies serve as a useful diagnostic tool, but their actual role in causing neuronal injury and clinical disease remains unclear. Further understanding of immunopathogenesis awaits successful experimental models. Among different syndromes, a varied proportion of patients shows neurologic improvement with immunosuppressive treatments; it is likely that many patients have already suffered irreversible neuronal injury at the time of diagnosis.

Acquired peripheral neuropathy

This article reviews the acquired causes of polyneuropathy other than diabetic and acute-onset neuropathies. The author gives a general method to simplify the diagnosis of chronic polyneuropathy. The acquired polyneuropathies are discussed under four main headings: metabolic disorders, toxic or deficiency states, infections, and immune-mediated. Recent advances in therapy are emphasized, and some illustrative case histories are provided.

Paraneoplastic neuromuscular syndromes

Although paraneoplastic syndromes are rare, a number of well- defined, neuromuscular paraneoplastic syndromes have been described and their pathophysiology listed. Many different malignancies have been associated with these syndromes, but small-cell lung cancer is the most common. Features shared by these conditions include onset of the underlying malignancy, rapid progression, severe disability, and the potential for some improvement, owing to treatment of the cancer. This article discusses Lambert-Eaton myasthenic syndrome, motor neuron disorders, peripheral neuropathies, and disorders of continuous muscle fiber activity, such as Stiffman syndrome.

Neuropathic arthropathy caused by paraneoplastic sensory neuropathy. A case report

Neuropathic arthropathy of both knees after paraneoplastic sensory neuropathy developed in a 64-year-old woman. The patient was found to have small cell lung cancer 2 months after the onset of a sensory neuropathy that was diagnosed as paraneoplastic sensory neuropathy, a nonmetastatic neurologic complication in patients with malignancy. The onset of paraneoplastic sensory neuropathy was followed by the gradual onset of neuropathic arthropathy. This is the first well documented report on neuropathic arthropathy in a patient with paraneoplastic sensory neuropathy.

Sensory neuropathies including painful and toxic neuropathies

In most peripheral neuropathies, dysfunction of motor and sensory nerve fibres is present. However, in some of them either pattern may predominate or be exclusively present. In this review we describe the clinical characteristics of sensory neuropathies, with emphasis on their possible causes. Guidelines are given for the diagnostic approach in these patients and, where possible, suggestions are given for treatment, including symptomatic treatment of painful neuropathies.