Polyneuropathy Associated with Age of Starting the Transfusion and Serum Ferritin Level in Iranian Patients with Thalassemia Major and Intermedia.

Considering the importance of managing patients with ß-thalassemia and the importance of early detection of disease complications, we examined the rate of sensorimotor neuropathy in patients with ß-thalassemia and the risk factors related to it. This cross-sectional study included 44 blood transfusion-dependent ß-thalassemia patients aged 5 years and older. Nerve conduction studies (NCSs) were performed via standard procedures for both motor and sensory nerves. Neuropathy was observed in 14 patients (31.8%). NCS results for sensorimotor nerves in patients were within normal range. In motor NCS results, increased ulnar nerve amplitude was observed in patients with increasing age, and peroneal nerve delay in patients with an increase in serum ferritin level (p < 0.05). In sensory NCS results, delayed ulnar and sural nerves latencies were found in patients with an increase in serum ferritin level (p < 0.05). We provide data that sensorimotor neuropathy exists in thalassemia patients. It seems that with the increase of serum ferritin level and the age of patients, neuropathy becomes more obvious, while other factors such as gender, body mass index, and the number of transfusions may not be associated with neuropathy.

Clinical relevance of testing for metabolic vitamin B12 deficiency in patients with polyneuropathy.

OBJECTIVE: Determine vitamin B12 threshold levels below which additional testing of methylmalonic acid (MMA) and/or homocysteine (Hcy) is useful to diagnose metabolic vitamin B12 deficiency in patients with polyneuropathy, and how vitamin B12, MMA and Hcy levels relate to the effect of supplementation therapy. METHODS: In a retrospective cohort study of 331 patients with polyneuropathy, vitamin B12, MMA and Hcy were measured. Linear regression models with vitamin B12 as dependent and Hcy or MMA as covariate were compared, to assess which was best related to vitamin B12. Threshold vitamin B12 levels for metabolic deficiency (defined as elevatede metabolites) were determined using logistic regression with elevated metabolites as dependent and vitamin B12 as covariate. A structured interview was conducted in 42 patients to evaluate response to vitamin B12 supplementation. RESULTS: MMA was best related to vitamin B12. Using elevated MMA for metabolic deficiency, we found 90% sensitivity at a vitamin B12 threshold level <264 pmol/L (358 pg/mL) and 95% sensitivity at <304 pmol/L (412 pg/mL). Improvement after supplementation was reported by 19% patients and stabilization by 24%. 88% of patients with improvement and 90% with stabilization either had absolute deficiency (Vitamin B12 < 148 pmol/L) or metabolic deficiency (elevated MMA and vitamin B12 ≥ 148 pmol/L). There were no additional patients with improvement or stabilization with isolated elevated Hcy. CONCLUSION: Testing of MMA has additional value in identifying patients with clinically relevant metabolic deficiency when vitamin B12 is below 304 pmol/L (412 pg/mL). Supplementation can be effective in patients with absolute and metabolic deficiency.

Vitamin B6 levels do not correlate with severity of neuropathy in chronic idiopathic axonal polyneuropathy.

Pyridoxine (vitamin B6) toxicity is known to cause a length-dependent, sensory predominant axonal polyneuropathy. There is debate regarding the threshold at which intake levels can cause neurological symptoms through pyridoxine toxicity. We asked if elevated plasma vitamin B6 levels were related to outcome measures in a well-characterized cohort of patients with chronic idiopathic axonal polyneuropathy (CIAP). We included 261 patients enrolled in the Peripheral Neuropathy Research Registry who had a complete dataset including a plasma vitamin B6 value. Patients with vitamin B6 deficiency (0-4.9 µg/L) were excluded. We performed a chi-square test for independence and analyzed the logistic relation of elevated plasma B6 level to nerve conduction studies (NCS), neurological examination findings, and patient-reported symptoms controlling for age and time elapsed since neuropathy symptom onset. Plasma B6 level was not related to neuropathy severity. There was no logistic relation of elevated plasma B6 level to NCS results, examination features including toe strength, vibration sense, and deep tendon reflexes, or patient-reported numbness or pain intensity. This study suggests that moderately elevated plasma B6 levels, even in the 100 to 200 µg/L range, are not associated with significantly worse neuropathy signs or symptoms. Although standard supplementation of B6 does not appear to have a major negative affect on CIAP, this study does not directly answer whether stopping supplementation will have a beneficial effect. Very few patients in the study had vitamin B6 levels >300 µg/L, suggesting that screening for vitamin B6 toxicity may be left to the discretion of the physician.

Vitamin B12 Deficiency Anemia and Polyneuropathy Due to Chronic Radiation Enteritis.

A 62-year-old Japanese woman developed numbness of the extremities and megaloblastic anemia. She had undergone total abdominal hysterectomy, whole-pelvis radiation therapy and chemotherapy for gynecological cancer 10 years before. Chronic abdominal pain, diarrhea and intermittent small-bowel obstruction had afflicted her for a long time. We diagnosed her with vitamin B12 deficiency anemia and polyneuropathy due to chronic radiation enteritis causing malabsorption. Vitamin B12 injections improved her numbness and anemia. The early diagnosis and treatment of deficiency of vitamin B12 are important. Physicians should regularly measure vitamin B12 levels and supplement vitamin B12 as needed in patients with chronic radiation enteritis.

Beta-thalassemia major complicated by intracranial hemorrhage and critical illness polyneuropathy.

Intracranial hemorrhage (ICH) is rarely seen in patients with thalassemia. A seven-year-old male, known case of beta-thalassemia major, on irregular packed cell transfusions (elsewhere) and non-compliant with chelation therapy, presented with congestive cardiac failure (Hb-3 gm/dl). He received three packed red cell transfusions over 7 days (cumulative volume 40 cc/kg). On the 9th day, he developed projectile vomiting and two episodes of generalized tonic-clonic convulsions with altered sensorium. He had exaggerated deep tendon reflexes and extensor plantars. CT-scan of brain revealed bilateral acute frontal hematoma with diffuse subarachnoid hemorrhage (frontal and parietal). Coagulation profile was normal. CT-angiography of brain showed diffuse focal areas of reduced caliber of anterior cerebral, middle cerebral, and basilar and internal carotid arteries (likely to be a spasmodic reaction to subarachnoid hemorrhage). He required mechanical ventilation for 4 days and conservative management for the hemorrhage. However, on the 18th day, he developed one episode of generalized tonic-clonic convulsion and his sensorium deteriorated further (without any new ICH) and required repeat mechanical ventilation for 12 days. On the 28th day, he was noticed to have quadriplegia (while on a ventilator). Nerve conduction study (42nd day) revealed severe motor axonal neuropathy (suggesting critical illness polyneuropathy). He improved with physiotherapy and could sit upright and speak sentences at discharge (59th day). The child recovered completely after 3 months. It is wise not to transfuse more than 20 cc/kg of packed red cell volume during each admission and not more than once in a week (exception being congestive cardiac failure) for thalassemia patients.

Genetic assessment and folate receptor autoantibodies in infantile-onset cerebral folate deficiency (CFD) syndrome.

INTRODUCTION: Cerebral folate deficiency (CFD) syndromes are defined as neuro-psychiatric conditions with low CSF folate and attributed to different causes such as autoantibodies against the folate receptor-alpha (FR) protein that can block folate transport across the choroid plexus, FOLR1 gene mutations or mitochondrial disorders. High-dose folinic acid treatment restores many neurologic deficits. STUDY AIMS AND METHODS: Among 36 patients from 33 families the infantile-onset CFD syndrome was diagnosed based on typical clinical features and low CSF folate. All parents were healthy. Three families had 2 affected siblings, while parents from 4 families were first cousins. We analysed serum FR autoantibodies and the FOLR1 and FOLR2 genes. Among three consanguineous families homozygosity mapping attempted to identify a monogenetic cause. Whole exome sequencing (WES) was performed in the fourth consanguineous family, where two siblings also suffered from polyneuropathy as an atypical finding. RESULTS: Boys (72%) outnumbered girls (28%). Most patients (89%) had serum FR autoantibodies fluctuating over 5-6 weeks. Two children had a genetic FOLR1 variant without pathological significance. Homozygosity mapping failed to detect a single autosomal recessive gene. WES revealed an autosomal recessive polynucleotide kinase 3´phosphatase (PNKP) gene abnormality in the siblings with polyneuropathy. DISCUSSION: Infantile-onset CFD was characterized by serum FR autoantibodies as its predominant pathology whereas pathogenic FOLR1 gene mutations were absent. Homozygosity mapping excluded autosomal recessive inheritance of any single responsible gene. WES in one consanguineous family identified a PNKP gene abnormality that explained the polyneuropathy and also its contribution to the infantile CFD syndrome because the PNKP gene plays a dual role in both neurodevelopment and immune-regulatory function. Further research for candidate genes predisposing to FRα-autoimmunity is suggested to include X-chromosomal and non-coding DNA regions.

Suramin-Induced Neurotoxicity: Preclinical Models and Neuroprotective Strategies.

Suramin is a trypan blue analogon originally developed to treat protozoan infections, which was found to have diverse antitumor effects. One of the most severe side effects in clinical trials was the development of a peripheral sensory-motor polyneuropathy. In this study, we aimed to investigate suramin-induced neuropathy with a focus on calcium (Ca2+) homeostasis as a potential pathomechanism. Adult C57Bl/6 mice treated with a single injection of 250 mg/kg bodyweight suramin developed locomotor and sensory deficits, which were confirmed by electrophysiological measurements showing a predominantly sensory axonal-demyelinating polyneuropathy. In a next step, we used cultured dorsal root ganglia neurons (DRGN) as an in vitro cell model to further investigate underlying pathomechanisms. Cell viability of DRGN was significantly decreased after 24-hour suramin treatment with a calculated IC50 of 283 µM. We detected a suramin-induced Ca2+ influx into DRGN from the extracellular space, which could be reduced with the voltage-gated calcium channel (VGCC) inhibitor nimodipine. Co-incubation of suramin and nimodipine partially improved cell viability of DRGN after suramin exposure. In summary, we describe suramin-induced neurotoxic effects on DRGN as well as potentially neuroprotective agents targeting intracellular Ca2+ dyshomeostasis.

Non-alcoholic Wernicke's encephalopathy with cortical involvement and polyneuropathy following gastrectomy.

In this study, we present the clinical manifestations, brain magnetic resonance imaging (MRI) and concurrent polyneuropathies in two patients with non-alcoholic Wernicke's encephalopathy (WE) after gastrojejunostomy (Billroth II) anastomosis procedures. These patients developed sub-acute onset of disorientation and disturbance of consciousness following several weeks of poor intake. Peripheral neuropathy of varying severity was noted before and after the onset of WE. Brain MRI of the patients showed cerebellar vermis and symmetric cortical abnormalities in addition to typical WE changes. Electrophysiological studies demonstrated axonal sensorimotor polyneuropathy. Prompt thiamine supplement therapy was initiated and both patients gradually recovered, however mild amnesia was still noted 6 months later. We reviewed non- alcoholic WE with atypical cortical abnormalities in English language literatures and identified 29 more cases. Eight out of 31 (25.8%) patients died during follow-up. Nine patients with gait disturbance or motor paresis had showed hyporeflexia in neurological examinations. In addition to classic triad, seizure was recorded in seven patients. Dietary deprivation is a risk factor for non-alcoholic WE among elderly patients receiving gastrointestinal surgery. The prognosis is good after thiamine supplement therapy. Recognizing the MRI features and predisposing factors in patients who have undergone gastrectomy can aid in the diagnosis and management.

[Efficiency of therapeutically applied physical factors for vibration disease caused by exposure to local vibration (review of literature).]

Important role in treatment and prophylaxis for vibration disease due to local vibration is played by physical factors. If high frequency components prevalent in occupational vibration, treatment with electric therapy, laser, magnetic fields, lymphatic drainage, hydrotherapy provides influence on leading chains of systemic microangiopathies pathogenesis - dysbalance of regulation influences by vegetative nervous system, vasoconstriction and intravascular changes, vascular permeability and microcirculation disorders. If low frequency coomponents prevalent in occupational vibration, treatment of polyneuropathies and locomotory disorders incorporates trophic processes activation: transcranial electroanalgesia, surface application of mineral waters, manual and subwater massage, ozone therapy, local spark discharges, peloids. Complex use of physical methods also increases human adaptational resources.

Madelung's disease associated with polyneuropathy and symptomatic hypokalemia.

Madelung's disease (multiple symmetric lipomatosis) is a rare disease characterized by abnormal diffuse lipomatosis in proximal upper limbs and neck. Previous reports have shown that this disease is associated with alcoholism, polyneuropathy, mitochondrial disease, and glucose intolerance. Here, we describe a 46-year-old man having Madelung's disease associated with polyneuropathy and symptomatic hypokalemia. He presented with insidious-onset weakness and numbness in lower limbs for 7 years and recent deterioration of symptoms. Proximal weakness improved with potassium supplement. Our observation may extend the phenotype of Madelung's disease to hypokalemic periodic paralysis.

Comparison of melatonin and oxytocin in the prevention of critical illness polyneuropathy in rats with experimentally induced sepsis.

BACKGROUND: Critical illness polyneuropathy is an acute neuromuscular disorder of critically ill patients and is characterized by limb and respiratory muscle weakness. The purpose of the study was to evaluate the neuroprotective effects of melatonin (MEL) and oxytocin (OT) on the early stage of sepsis by recording compound muscle action potentials and measuring plasma tumor necrosis factor (TNF)-α levels, lipid peroxidation (malondialdehyde; MDA), and total antioxidant capacity. MATERIALS AND METHODS: One hundred adult male Sprague-Dawley rats were included in the study. The cecal ligation and puncture (CLP) procedure was performed to induce the sepsis model. MEL (10, 20, and 40 mg/kg), OT (0.4, 0.8, and 1.6 mg/kg), and a combination of MEL (20 mg/kg) and OT (0.8 mg/kg) were administered intraperitoneally in the first hour of surgery. Electromyography (EMG) studies were achieved 24 h after CLP surgery and then blood samples were collected for biochemical measurements. RESULTS: EMG findings revealed that compound muscle action potential amplitude was significantly decreased and distal latency was prolonged in the CLP group compared with the sham group (P < 0.05 and P < 0.0005). Moreover, the animals that received CLP surgery showed significantly higher TNF-α and MDA levels and lower total antioxidant capacity values than the sham group. The administration of MEL and OT to rats significantly abolished the EMG alterations and suppressed oxidative stress and TNF-α release in CLP-induced rats. CONCLUSIONS: The inflammatory processes and imbalance in oxidative/antioxidative status play important roles in the pathogenesis of critical illness polyneuropathy. We suggest that both oxytocin and melatonin may have beneficial effects against sepsis-induced polyneuropathy in critical illness.

The significance of folate deficiency in alcoholic and nutritional neuropathies: analysis of a case.

OBJECTIVE: To elucidate the significance of folate deficiency in alcoholic and nutritional neuropathies. METHODS: We preformed a comprehensive clinical screening of a patient with chronic alcoholism who manifested neuropathy, macrocytic anemia, liver dysfunction, and folate deficiency. RESULTS: A 33-y-old woman with chronic alcoholism presented with acutely progressive glove- and stocking-type sensorimotor polyneuropathy. Although an episode of neuropathy preceded the current episode by 2 y, its cause was never determined. The findings of nerve conduction studies were indicative of axonal neuropathy. Laboratory findings revealed macrocytic anemia and liver dysfunction. Her serum level of folate was reduced, whereas thiamine, riboflavin, and cobalamin levels were within normal range. The neuropathy and anemia showed gradual recovery after the initiation of folic acid supplementation. CONCLUSIONS: This case study indicates that folate deficiency should be monitored closely in patients with chronic alcoholism and associated malnutrition. Additionally, folate deficiency should be considered as a differential diagnosis of neuropathy.

Respiratory dysfunction in ventilated patients: can inspiratory muscle training help?

Respiratory muscle dysfunction is associated with prolonged and difficult weaning from mechanical ventilation. This dysfunction in ventilator-dependent patients is multifactorial: there is evidence that inspiratory muscle weakness is partially explained by disuse atrophy secondary to ventilation, and positive end-expiratory pressure can further reduce muscle strength by negatively shifting the length-tension curve of the diaphragm. Polyneuropathy is also likely to contribute to apparent muscle weakness in critically ill patients, and nutritional and pharmaceutical effects may further compound muscle weakness. Moreover, psychological influences, including anxiety, may contribute to difficulty in weaning. There is recent evidence that inspiratory muscle training is safe and feasible in selected ventilator-dependent patients, and that this training can reduce the weaning period and improve overall weaning success rates. Extrapolating from evidence in sports medicine, as well as the known effects of inspiratory muscle training in chronic lung disease, a theoretical model is proposed to describe how inspiratory muscle training enhances weaning and recovery from mechanical ventilation. Possible mechanisms include increased protein synthesis (both Type 1 and Type 2 muscle fibres), enhanced limb perfusion via dampening of a sympathetically-mediated metaboreflex, reduced lactate levels and modulation of the perception of exertion, resulting in less dyspnoea and enhanced exercise capacity.

Muscle weakness in septic patients requiring mechanical ventilation: protective effect of transcutaneous neuromuscular electrical stimulation.

PURPOSE: The aim of this study was to evaluate the effect of transcutaneous neuromuscular electrical stimulation (NMES) on muscle strength in septic patients requiring mechanical ventilation (MV). METHODS: Sixteen septic patients requiring MV and having 1 or more organ failure other than respiratory dysfunction were enrolled within 48 hours from admission to the intensive care unit. Neuromuscular electrical stimulation was administered twice a day on brachial biceps and vastus medialis (quadriceps) of 1 side of the body until MV withdrawal. Blinded investigators measured arm and thigh circumferences, biceps thickness by ultrasonography, and muscle strength after awakening with Medical Research Council scale. RESULTS: Two patients died before strength evaluation and were excluded from the analysis. Neuromuscular electrical stimulation was applied for 13 days (interquartile range, 7-30 days). Biceps (P = .005) and quadriceps (P = .034) strengths were significantly higher on the stimulated side at the last day of NMES. Improvement was mainly observed in more severe and weaker patients. Circumference of the nonstimulated arm decreased at the last day of NMES (P = .015), whereas no other significant differences in limb circumferences or biceps thickness were observed. CONCLUSION: Neuromuscular electrical stimulation was associated with an increase in strength of the stimulated muscle in septic patients requiring MV. Neuromuscular electrical stimulation may be useful to prevent muscle weakness in this population.

[Using transcranial electric stimulation in patients with occupational disorders of the nervous system].

The paper presents the results of transcranial electrical stimulation (TES) in treating patients with vibration disease and occupational lumbosacral radiculopathy. It is shown that the inclusion of TES in the program of rehabilitation therapy gives a more pronounced clinical effect, helps to reduce pain, has psychological correcting antidepressant action significantly, improves the quality of life of patients. The study results enable to recommend TES in the complex medical and rehabilitative measures as an effective and pathogenetically substantiated method of treatment of patients with occupational diseases of the nervous system.

[Original articles on axonal neuropathy in 2010]. / Les actualités sur les polyneuropathies axonales en 2010.

During 2010, 15 articles were published which focused on chronic sensorimotor axonal neuropathy; some will be discussed in this review. Clinical diagnosis from signs and symptoms seems to be excessively variable, often overestimating the incidence of diabetic sensorimotor polyneuropathy. Long-term use of Metformin is associated with malabsorption of vitamin B12. Metformin exposure may be a iatrogenic cause for exacerbation of peripheral neuropathy in patients with type 2 diabetes. The neuroprotective role of vitamin E against cisplatinperipheral neurotoxicity has been suggested by a phase III study. Metallosis after hip arthroplasty with a cobalt-chromium alloy prosthesis can cause progressive sensory disturbance, hearing loss and hypothyroidism. The effects of electrical stimulation on neuromuscular recovery after nerve crush injury in rats do not support a benefit of the tested protocol using electrical stimulation during the period of motor nerve recovery following injury. The rate of motor vehicle accidents in patients with neuropathy, based on surveys from 260 subjects, demonstrated that 40.6% were involved in traffic accidents. Accident frequency and discomfort with driving are higher in neuropathy patients compared to age-matched national statistics. Peripheral neuropathy in primary (AL) amyloidosis may be the cause of stepwise progressive, multiple upper limb mononeuropathies.

Current concepts in the management of diabetic polyneuropathy.

Approximately one in three people with diabetes is affected by diabetic distal symmetric sensorimotor polyneuropathy (DSPN), which represents a major health problem as it may present with excruciating neuropathic pain and is responsible for substantial morbidity, increased mortality and impaired quality of life. Neuropathic pain causes considerable interference with sleep, daily activities, and enjoyment of life. Treatment is based on four cornerstones: (1) intensive diabetes therapy and multifactorial risk intervention; (2) treatment based on pathogenetic mechanisms; (3) symptomatic treatment; and (4) avoidance of risk factors and complications. Recent experimental studies suggest a multifactorial pathogenesis of diabetic neuropathy. From the clinical point of view, it is important to note that, based on these pathogenetic mechanisms, therapeutic approaches could be derived, some of which are currently being evaluated in clinical trials. Management of chronic painful DSPN remains a challenge for the physician and should consider the following practical rules: the appropriate and effective drug has to be tried and identified in each patient by carefully titrating the dosage based on efficacy and side effects; lack of efficacy should be judged only after 2-4 weeks of treatment using an adequate dosage. Analgesic combination therapy may be useful, and potential drug interactions have to be considered given the frequent polypharmacy in people with diabetes. Not only increased alcohol consumption but also the traditional cardiovascular risk factors such as visceral obesity, hypertension, hyperlipidemia and smoking have a role in the development and progression of diabetic neuropathy and hence need to be prevented or treated.

Neurological disorders associated with cassava diet: a review of putative etiological mechanisms.

Tropical ataxic neuropathy (TAN) and epidemic spastic paraparesis (konzo) are two neurological disorders associated with the consumption of cassava (Manihot esculenta) in several African countries. TAN is characterized by sensory polyneuropathy, sensory ataxia, bilateral optic atrophy and bilateral sensori-neural deafness. It occurs in elderly individuals subsisting on a monotonous cassava diet with minimal protein supplementation. Konzo is a syndrome of symmetrical spastic paraparesis with a predilection for children and young women and invariably associated with consumption of inadequately processed bitter cassava roots with minimal protein supplementation. Despite numerous epidemiological, clinical and biochemical studies aimed at elucidating the etiological mechanisms of these disorders, their etiologies remain unknown, and there is no known treatment. The diseases continue to be prevalent in endemic areas, causing significant disability and increased mortality. A fresh appraisal of the putative etiologic mechanisms proposed for these intriguing and enigmatic syndromes is presented in this paper. Evidences against a causal role for cyanide intoxication are discussed, and evidences implicating thiamine deficiency as a unifying etiological mechanism for these neurological syndromes are presented. It is concluded that urgent research is needed to evaluate thiamine status and implement a therapeutic trial of thiamine in these debilitating neurological disorders.

Unexplained chronic cough and vitamin B-12 deficiency.

BACKGROUND: Chronic cough is characterized by sensory neuropathy. Vitamin B-12 (cobalamin) deficiency (Cbl-D) causes central and peripheral nervous system damage and has been implicated in sensory neuropathy and autonomic nervous system dysfunction. OBJECTIVE: We evaluated whether Cbl-D has a role in chronic, unexplained cough. DESIGN: Laryngeal threshold (histamine concentration that provokes a 25% decrease in the midinspiratory flow), bronchial threshold (histamine concentration that provokes a 20% decrease in the forced expiratory volume in 1 s), and cough threshold (histamine concentration that causes ≥5 coughs) in response to an inhaled histamine were assessed in 42 patients with chronic, unexplained cough [27 Cbl-D patients and 15 patients without Cbl-D (Cbl-N)] before and after intramuscular injections of cobalamin for 2 mo. Laryngeal, bronchial, and cough hyperresponsiveness was diagnosed when histamine concentration thresholds were ≤8 mg/mL. Seven Clb-D and 3 Cbl-N patients underwent an oropharyngeal biopsy before treatment. RESULTS: Cbl-D patients had a higher prevalence of laryngeal hyperresponsiveness than did Cbl-N patients (92.6% compared with 66.7%; P = 0.03), a thinner oropharyngeal epithelium [133.7 µm (95% CI: 95, 172 µm) compared with 230.8 µm (95% CI: 224, 237 µm); P = 0.002], a lower number of myelinated nerve fibers [2.25/mm(2) (95% CI: 1.8, 2.7/mm(2)) compared with 3.44/mm(2) (95% CI: 3, 3.8/mm(2)); P = 0.05], and a higher immunoreactive score for nerve growth factor (NGF) [6.7 (95% CI: 6, 7.3) compared with 2.8 (95% CI: 2.5, 3.1); P = 0.02]. After cobalamin supplementation, symptoms and laryngeal, bronchial, and cough thresholds were significantly improved in Cbl-D but not in Cbl-N patients. CONCLUSIONS: This study suggests that Cbl-D may contribute to chronic cough by favoring sensory neuropathy as indicated by laryngeal hyperresponsiveness and increased NGF expression in pharyngeal biopsies of Cbl-D patients. Cbl-D should be considered among factors that sustain chronic cough, particularly when cough triggers cannot be identified.