Oxaliplatin rechallenge in metastatic colorectal cancer patients with clinically significant oxaliplatin‐induced peripheral neurotoxicity

We investigated whether rechallenge with oxaliplatin (OXA) can worsen the pre‐existing oxaliplatin‐induced peripheral neurotoxicity (OXAIPN) in metastatic colorectal cancer (mCRC) patients. Patients previously treated with OXA, having clinically significant grade 1 or 2 OXAIPN were assessed, after receiving rechallenge with OXA, using the clinical version of the Total Neuropathy Score (TNSc). Peripheral neuropathy was assessed at the end of first OXA exposure and at completion of OXA rechallenge. The first line OXA‐based chemotherapy was completed at least 9 months earlier (OXA‐free interval). We studied 25 mCRC patients, 14 males and 11 females, with a median age of 63 (35‐77) years. After their first exposure to OXA‐based chemotherapy, 9 (36%) patients developed grade 1 OXAIPN and 16 patients grade 2 (64%) neurotoxicity. OXA reintroduction with a median of 10 (8‐14) cycles led to grade 1 OXAIPN in two patients (8%), grade 2 in 19 patients (76%), and grade 3 neuropathy in 4 (16%) patients Worsening of pre‐existing OXAIPN was documented in seven (28%) patients and was significantly associated with higher OXA delivered cumulative dose (P < .001). Median TNSc scores following treatment (10; range 4‐18) were significantly increased (P < .001), when compared to the scores recorded at the end of first line treatment (8; range 2‐12). Rechallenging OXA appears to relatively worsen the severity of existing OXAIPN. However, the majority of rechallenged patients developed a clinically significant (grade 2) OXAIPN, rather than treatment‐emergent grade 3. As such, OXA rechallenge might be a feasible option in patients previously having OXAIPN.     

Real world,open label experience with lacosamide against acute painful oxaliplatin‐induced peripheral neurotoxicity

We report the outcome of a pilot, open‐label study that tested the potential of lacosamide (200 mg/bi.d) as an effective and safe symptomatic treatment against acute painful oxaliplatin‐induced peripheral neurotoxicity (OXAIPN). Lacosamide was introduced in 18 colorectal cancer patients with evidence of clinically significant acute, painful OXAIPN after infusion of the third course (T1) of oxaliplatin‐based chemotherapy (FOLFOX4) and was maintained until completion of all 12 courses (T4). The OXA‐Neuropathy Questionnaire (OXA‐NQ) was used to record the severity of acute OXAIPN; the PI‐NRS estimated the severity of neuropathic pain, while the chronic OXAIPN was graded with TNSc. The EuroQOL ( EQ‐5D) instrument was also applied. The Patient Global Impression of Change (PGIC) scale measured the lacosamide‐attributed perception of change. LCM‐responders were considered those with ≥50% reduction in PI‐NRS and OXA‐NQ scores at T4, compared to T1. Patients experienced on T1 a median number of acute OXAIPN symptoms of 4 and had a median neuropathic pain severity score of 6, which was strongly related to lower quality of life, according to EQ‐VAS (P < .001). At T4, 12 patients (66.7%) were classified as responders. A significant clinical improvement was documented in the severity of acute OXAIPN and neuropathic pain in relation to lacosamide (P < .001) at T4 compared to T1, which was associated with improved EQ‐VAS scores (P < .001). Twelve patients scored PGIC ≥5 (lacosamide‐attributed) at T4. There were no incidences of early drop‐outs for safety reasons. Lacosamide appears to be an effective and well‐tolerated symptomatic treatment against acute, painful OXAIPN.     

Genetic determinants of chronic oxaliplatin‐induced peripheral neurotoxicity: a genome‐wide study replication and meta‐analysis

We aimed at validating the role of genetic variants identified by a recent genome‐wide association study (GWAS) as determinants of chronic oxaliplatin‐induced peripheral neurotoxicity (OXAIPN). Eight polymorphisms (rs10486003, rs2338, rs843748, rs797519, rs4936453, rs12023000, rs17140129, and rs6924717) were genotyped in a total of 150 colorectal cancer patients of Caucasian origin receiving oxaliplatin‐based chemotherapy. The severity grade of chronic OXAIPN was assessed by NCI‐CTC criteria and the clinical version of the Total Neuropathy Score^© (TNSc^©). None of the polymorphisms investigated was found associated with grade ≥ 2 chronic OXAIPN (NCI‐CTC criteria), while a nominal association emerged for ACYP2 rs843748 when using the TNSc^© scale (dominant model: odds ratio [OR]: 0.27, 95% confidence interval [CI]: 0.10–0.75, P = 0.008). In the combined analysis of this results with data of the two previously published studies which assessed chronic OXAIPN by NCI‐CTC criteria, evidence suggestive of association with chronic OXAIPN (NCI‐CTC criteria) was found for ACYP2 rs843748 (dominant model: OR: 2.40, 95%CI: 1.40–5.24, P = 0.027), which, however, did not remain significant after correction for multiple testing (threshold P‐value <0.00625). These findings suggest a minor role of the single nucleotide polymorphisms (SNPs) investigated as genetic determinants of chronic OXAIPN. These results also highlight the importance of replication studies with meta‐analysis for validation of GWAS findings.     

Liability of the voltage‐gated potassium channel KCNN3 repeat polymorphism to acute oxaliplatin‐induced peripheral neurotoxicity

Thus far, there are conflicting results on the causal role of K+ channels in the pathogenesis of acute oxaliplatin‐induced peripheral neurotoxicity (OXAIPN). As such, we tested the hypothesis that the voltage‐gated K+ channel KCNN3 repeat polymorphism confers liability to acute OXAIPN. DNA from 151 oxaliplatin‐treated patients for colorectal cancer was extracted and genotyped. The incidence of acute OXIPN was measured by the OXA‐neuropathy questionnaire, while the severity of acute OXAIPN was scored basing on the number of symptoms reported by the patients at each clinical assessment. The increased number of acute symptoms was considered as being suggestive of an increased severity of acute OXAIPN. A total of 130/151 (86.1%) patients developed any grade of acute OXAIPN. Grade I acute neurotoxicity was revealed in 43 (28.5%) patients; grade II in 34 (22.5%); and grade III in 53 (53.1%) patients. Genotyping revealed alleles carrying 11 to 20 CAG repeats. The majority of patients were heterozygous (131; 89.4%). The most common numbers of CAG repeats were 15 (n = 46), 16 (n = 53), and 17 (n = 95). Patients carrying alleles with either 15 to 17 CAG repeats (P = .601) did not experience a higher incidence of grade III (treatment‐emergent) acute OXAIPN. Likewise, no increased incidence of acute treatment‐emergent OXAIPN was noted in heterozygous patients carrying either two short alleles (<19 CAG repeats) or one short and one long (≥19 CAG repeats) allele (P = .701). Our results do not support a causal relationship between the KCNN3CAG repeat polymorphism and acute OXΑIPN.     

Integrin beta‐3 L33P: a new insight into the pathogenesis of chronic oxaliplatin‐induced peripheral neuropathy?

Aim: To assess the significance of the ITGB3 polymorphism at residue 33 (ITGB3 L33P) in the development of chronic oxaliplatin‐induced peripheral neuropathy (OXLIPN). Methods: Fifty‐five patients with advanced colorectal cancer were genotyped, using allele‐specific primers and sybr green in real‐time PCR. Patients had received adjuvant oxaliplatin‐based chemotherapy. The severity of the OXLIPN was defined by means of the clinical total neuropathy score (TNSc). Following the discontinuation of treatment, 34/55 patients (61.8%) developed OXLIPN. Grade I neurotoxicity was revealed in 13 (38.2%) patients and grade II neurotoxicity in 21 (61.8%) patients. Results: Patients without OXLIPN (n = 21) were 19% homozygous for C, 33.3% were heterozygous, and 47.7% were homozygous for T. The corresponding percentages for patients developing any grade of OXLIPN (n = 34) were similar. About half of patients (46.1%) with grade I OXLIPN were heterozygotes (CT), 23.1% were CC, and 30.8% were TT. The majority of patients with grade II OXLIPN were TT (66.7%) with the remaining 33.3% being CT. The TT genotype was associated with increased severity of OXLIPN compared to the genotypes containing the C allele (P = 0.044). Conclusion: The ITGB3 L33P seems to be unrelated to the development of OXLIPN, but it appears to be related to its severity.     

Platinum‐induced peripheral neurotoxicity: From pathogenesis to treatment

Platinum‐induced peripheral neurotoxicity (PIPN) is a common side effect of platinum‐based chemotherapy that may cause dose reduction and discontinuation, with oxaliplatin being more neurotoxic. PIPN includes acute neurotoxicity restricted to oxaliplatin, and chronic non‐length‐dependent sensory neuronopathy with positive and negative sensory symptoms and neuropathic pain in both upper and lower limbs. Chronic sensory axonal neuropathy manifesting as stocking‐and‐glove distribution is also frequent. Worsening of neuropathic symptoms after completing the last chemotherapy course may occur. Motor and autonomic involvement is uncommon. Ototoxicity is frequent in children and more commonly to cisplatin. Platinum‐based compounds result in more prolonged neuropathic symptoms in comparison to other chemotherapy agents. Patient reported outcomes questionnaires, clinical evaluation and instrumental tools offer complementary information in PIPN. Electrodiagnostic features include diffusely reduced/abolished sensory action potentials, in keeping with a sensory neuronopathy. PIPN is dependent on cumulative dose but there is a large variability in its occurrence. The search for additional risk factors for PIPN has thus far yielded no consistent findings. There are currently no neuroprotective strategies to reduce the risk of PIPN, and symptomatic treatment is limited to duloxetine that was found effective in a single phase III intervention study. This review critically examines the pathogenesis, incidence, risk factors (both clinical and pharmacogenetic), clinical phenotype and management of PIPN.     

Serum micronutrients and prealbumin during development and recovery of chemotherapy‐induced peripheral neuropathy

Chemotherapy‐induced peripheral neuropathy (CIPN) is a frequent adverse event. Nutritional status can become impaired in cancer patients, potentially contributing to neuropathy's evolution. Our aim was to evaluate serum micronutrients and prealbumin in a cohort of 113 solid‐cancer patients receiving platinum and taxane compounds during the development and recovery of neuropathy, up to 1 year after finishing treatment. CIPN was graded according to Total Neuropathy Score^© and NCI.CTCv3 at T0 (baseline), T1 (1–3 months), and T12 (12 months) after chemotherapy. CIPN was classified as asymptomatic (< grade 2) or symptomatic (≥2). CIPN recovery was defined as ≥1 grade improvement at T12. Symptomatic CIPN developed in 52% of patients. Symptomatic patients presented a higher increase in TNSc (p < 0.001), in TNSr^© (p < 0.001), and decrease in sural (p < 0.001) and radial nerve conduction (p < 0.001). No significant differences with any of the micronutrients were observed along T0‐T1 period between severity or chemotherapy groups. By T12, symptomatic patients without recovery had a decrease in vitamin E levels (p = 0.019) and prealbumin (p = 0.062) compared with those symptomatic that improved. A correlation between the variation of vitamin E and prealbumin at T0‐T1 (r = 0.626, p = 0.001) and T1‐T12 (r = 0.411, p = 0.06) was observed. After chemotherapy treatment, the improvement of patients displaying symptomatic neuropathy is related to vitamin E and prealbumin serum levels. Our results suggest that nutritional status can play a role in CIPN recovery.     

Effects of oxaliplatin and oleic acid Gc‐protein‐derived macrophage‐activating factor on murine and human microglia

The biological properties and characteristics of microglia in rodents have been widely described, but little is known about these features in human microglia. Several murine microglial cell lines are used to investigate neurodegenerative and neuroinflammatory conditions; however, the extrapolation of the results to human conditions is frequently met with criticism because of the possibility of species‐specific differences. This study compares the effects of oxaliplatin and of oleic acid Gc‐protein‐derived macrophage‐activating factor (OA‐GcMAF) on two microglial cell lines, murine BV‐2 cells and human C13NJ cells. Cell viability, cAMP levels, microglial activation, and vascular endothelial growth factor (VEGF) expression were evaluated. Our data demonstrate that oxaliplatin induced a significant decrease in cell viability in BV‐2 and in C13NJ cells and that this effect was not reversed with OA‐GcMAF treatment. The signal transduction pathway involving cAMP/VEGF was activated after treatment with oxaliplatin and/or OA‐GcMAF in both cell lines. OA‐GcMAF induced a significant increase in microglia activation, as evidenced by the expression of the B7‐2 protein, in BV‐2 as well as in C13NJ cells that was not associated with a concomitant increase in cell number. Furthermore, the effects of oxaliplatin and OA‐GcMAF on coculture morphology and apoptosis were evaluated. Oxaliplatin‐induced cell damage and apoptosis were nearly completely reversed by OA‐GcMAF treatment in both BV‐2/SH‐SY5Y and C13NJ/SH‐SY5Y cocultures. Our data show that murine and human microglia share common signal transduction pathways and activation mechanisms, suggesting that the murine BV‐2 cell line may represent an excellent model for studying human microglia. © 2015 Wiley Periodicals, Inc.     

Paraparetic Guillain‐Barré syndrome: Nondemyelinating reversible conduction failure restricted to the lower limbs

Introduction: Paraparetic Guillain‐Barré syndrome (GBS) is a rare subtype of GBS characterized by leg weakness and areflexia in the absence of neurological involvement of the arms, cranial nerves, or respiratory muscles. Onset is characterized by lower back, buttock, or leg pain, followed by development of symmetric flaccid limb weakness in the absence of sensory disturbance. Methods: We describe an elderly woman who developed postinfectious symmetric flaccid leg weakness in the absence of sensory disturbance. Serial nerve conduction studies were carried out over 5 months. Results: Antecedent infection, a monophasic disease course, and the presence of cerebrospinal fluid albuminocytological dissociation suggested a diagnosis of paraparetic GBS. Serial nerve conduction studies demonstrated nondemyelinating reversible conduction failure, which was restricted to the legs. Axonal neuropathy was supported by the presence of anti‐GM1 IgG antibodies. Conclusions: These findings suggest that patients with paraparetic GBS have axonal neuropathy, which is restricted to the lower limbs. Muscle Nerve 55 : 281–285, 2017     

Does forearm mixed nerve conduction velocity reflect retrograde changes in carpal tunnel syndrome?

The mixed nerve conduction velocity of the median nerve in the forearm diverged from the motor and sensory nerve conduction velocities and correlated poorly with the severity of carpal tunnel syndrome (CTS) in 61 hands. In contrast, the motor and sensory nerve conduction velocities in the forearm correlated well with CTS severity. The mixed nerve conduction velocity in the forearm is probably determined by nonlesioned fibers such as those from the cutaneous palmar branch of the median nerve. The motor and sensory, but not the mixed nerve conduction velocities in the forearm may be used to estimate possible retrograde impairment in CTS. © 1994 John Wiley & Sons, Inc.     

Multimodal quantitative examination of nerve function in colorectal cancer patients prior to chemotherapy

Introduction: Given recent findings of subclinical sensory deficits in colorectal cancer patients before oxaliplatin treatment, in the current study we aimed to identify evidence of subclinical peripheral neuropathy on multimodal testing before chemotherapy commencement. Methods: Clinical, functional, and neurophysiological assessments were undertaken in 93 colorectal cancer patients before chemotherapy. Results: There was no neurophysiological evidence of neuropathy, with 92 of 93 sural sensory values within normative reference values for age and no significant abnormalities detected in nerve conduction or nerve excitability studies. Clinical neurological assessment revealed 75.9% of patients with no signs or symptoms, 10.3% with reduction in distal vibration or pinprick sensitivity, and 6.9% with reduction in ankle reflexes only. There was no difference in manual dexterity (using the 9‐hole peg‐board test) compared with normative data. Discussion: The present study has established a low likelihood of significant distal symmetrical polyneuropathy in colorectal cancer patients before initiation of chemotherapy. Muscle Nerve 57 : 615–621, 2018     

Whole‐exome sequencing reveals a novel missense mutation in the MARS gene related to a rare Charcot‐Marie‐Tooth neuropathy type 2U

Charcot‐Marie‐Tooth (CMT) is a heterogeneous group of progressive disorders, characterized by chronic motor and sensory polyneuropathy. This hereditary disorder is related to numerous genes and varying inheritance patterns. Thus, many patients do not reach a final genetic diagnosis. We describe a 13‐year‐old girl presenting with progressive bilateral leg weakness and gait instability. Extensive laboratory studies and spinal magnetic resonance imaging scan were normal. Nerve conduction studies revealed severe lower limb peripheral neuropathy with prominent demyelinative component. Following presumptive diagnosis of chronic inflammatory demyelinating polyneuropathy, the patient received treatment with steroids and intravenous immunoglobulins courses for several months, with no apparent improvement. Whole‐exome sequencing revealed a novel heterozygous c.2209C>T (p.Arg737Trp) mutation in the MARS gene (OMIM 156560). This gene has recently been related to CMT type 2U. In‐silico prediction programs classified this mutation as a probable cause for protein malfunction. Allele frequency data reported this variant in 0.003% of representative Caucasian population. Family segregation analysis study revealed that the patient had inherited the variant from her 60‐years old mother, reported as healthy. Neurologic examination of the mother demonstrated decreased tendon reflexes, while nerve conduction studies were consistent with demyelinative and axonal sensory‐motor polyneuropathy. Our report highlights the importance of next‐generation sequencing approach to facilitate the proper molecular diagnosis of highly heterogeneous neurologic disorders. Amongst other numerous benefits, this approach might prevent unnecessary diagnostic testing and potentially harmful medical treatment.     

Early electrophysiological findings in acute inflammatory demyelinating polyradiculoneuropathy variant of Guillain‐Barre syndrome in the Pakistani population – a comparison with global data

Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and acute motor axonal neuropathy are the most common variants of Guillian‐Barre syndrome documented in the Asian population. However, the variability of early neurophysiologic findings in the Asian population compared to western data has not been documented. Eighty‐seven cases of AIDP were retrospectively reviewed for their demographic, clinical, electrophysiological, and laboratory data. Mean age of subjects was 31 ± 8 years with males more commonly affected. Motor symptoms (97%) at presentation predominated. Common early nerve conduction findings included low motor amplitudes (85%), recordable sural sensory responses (85%), and absent H‐reflex responses (65%). Prolonged F‐latencies were found most commonly in posterior tibial nerves (23%) in the lower limbs and median and ulnar nerves (18%) in the upper limbs. Blink reflex (BR) studies were performed in 57 patients and were abnormal in 80% of those with clinical facial weakness and in 17 of 52 patients (33%) with no clinical cranial nerve signs, suggesting subclinical cranial nerve involvement. Abnormal motor and sensory amplitudes are seen early. Prolonged distal latencies, temporal dispersion/conduction blocks and sural sparing pattern are other common early nerve conduction study findings of AIDP seen in the Pakistani population. There are no significant differences in abnormalities of conduction velocities and delayed reflex responses compared to published data. The BR can help in the early diagnosis of AIDP.     

A novel mutation of LRSAM1 in a Chinese family with Charcot‐Marie‐Tooth disease

Charcot‐Marie‐Tooth (CMT) disease is the most common inherited peripheral neuropathy characterized by progressive distal muscle weakness and atrophy with decreased or absent tendon reflexes. Mutations in LRSAM1 have been identified to cause CMT disease type 2P. We report a novel LRSAM1 mutation c.2021‐2024del (p.E674VfsX11) in a Chinese autosomal dominant CMT disease type 2 family. The phenotype was characterized by late onset and mild sensory impairment. Electrophysiological findings showed normal or mildly to moderately reduced motor and sensory nerve conduction velocities in lower and upper limb nerves.     

Correlation of nerve ultrasound,electrophysiological, and clinical findings in post Guillain‐Barré syndrome

We aimed to correlate functional disability, electrophysiology, and nerve ultrasound in patients after Guillain‐Barré syndrome (GBS). Seventy‐five healthy controls and 41 post‐GBS patients (mean 3.4 years, SD ± 2.91 years after onset) underwent clinical, sonographic, and electrophysiological evaluation. Compared to healthy controls, the post‐GBS patients showed: (1) a mean Rasch‐built Overall Disability Scale score of 31.8 (SD ± 11.6), modified Rasch‐built fatigue severity scale score of 15.6 (SD ± 3.2), Medical Research Council sum score of 22 (SD ± 5.6); (2) electrophysiological signs of permanent axonal loss in the majority of the peripheral nerves; (3) sonographical evidence of higher cross‐sectional area values (CSA) of the ulnar (elbow, p < 0.001), radial (spiral groove, p < 0.001), tibial nerve (popliteal fossa, p < 0.001) and brachial plexus (supraclavicular space, p < 0.001). No correlation between sonographic and electrophysiological findings was found. Neither nerve ultrasound nor electrophysiology correlated with muscle strength, overall disability, and fatigue scale. Compared to healthy controls, post‐GBS patients had significant functional disability. Despite significant abnormalities in both electrophysiology and ultrasound compared to healthy controls, neither electrophysiology nor nerve ultrasound correlated with functional disability of these patients.     

Characteristics of bortezomib‐ and thalidomide‐induced peripheral neuropathy

Abstract Dose‐limiting peripheral neuropathy (PN) is frequently reported with the use of thalidomide and bortezomib, novel proteasome inhibitors. While these two agents have significant activity in multiple myeloma (MM), the combination and the associated PN have not been fully examined in untreated patients. The objective of this study was to report the baseline prevalence and occurrence of PN in newly diagnosed MM patients treated with bortezomib and thalidomide. Twenty‐seven patients (11 men and 16 women) with previously untreated MM were prospectively monitored for PN. Total neuropathy score reduced (TNSr) was calculated at baseline and after every two cycles of bortezomib treatment. The median cumulative dose of bortezomib was 35.6 mg/m² (median 8 cycles) and of thalidomide was 16.8 g. Only three subjects showed mild PN at baseline (whole group median TNSr 0). At the end of treatment, PN developed in 26 patients (median TNSr 8). PN was of mild to moderate severity (TNSr grade 1 = 11, grade 2 = 10, grade 3 = 5, and grade 4 = 0). Nerve conduction studies showed axonal physiology in all except three subjects in whom demyelinating physiology was noted. The median TNSr was 17 in the demyelinating group and 9 in the axonal group. There was no significant correlation of TNSr with cumulative bortezomib or thalidomide dose. At follow‐up, 80% of patients had become asymptomatic after discontinuation of the chemotherapy. We conclude that bortezomib and thalidomide combination chemotherapy induces a reversible length‐dependent sensory>motor, predominantly axonal, large‐fiber>small‐fiber polyneuropathy. In a subset, a more severe demyelinating polyneuropathy may develop.     

Phrenic nerve involvement and respiratory muscle weakness in patients with Charcot‐Marie‐Tooth disease 1A

Diaphragm weakness in Charcot‐Marie‐Tooth disease 1A (CMT1A) is usually associated with severe disease manifestation. This study comprehensively investigated phrenic nerve conductivity, inspiratory and expiratory muscle function in ambulatory CMT1A patients. Nineteen adults with CMT1A (13 females, 47 ± 12 years) underwent spiromanometry, diaphragm ultrasound, and magnetic stimulation of the phrenic nerves and the lower thoracic nerve roots, with recording of diaphragm compound muscle action potentials (dCMAP, n = 15), transdiaphragmatic and gastric pressures (twPdi and twPgas, n = 12). Diaphragm motor evoked potentials (dMEP, n = 15) were recorded following cortical magnetic stimulation. Patients had not been selected for respiratory complaints. Disease severity was assessed using the CMT Neuropathy Scale version 2 (CMT‐NSv2). Healthy control subjects were matched for age, sex, and body mass index. The following parameters were significantly lower in CMT1A patients than in controls (all P < .05): forced vital capacity (91 ± 16 vs 110 ± 15% predicted), maximum inspiratory pressure (68 ± 22 vs 88 ± 29 cmH₂O), maximum expiratory pressure (91 ± 23 vs 123 ± 24 cmH₂O), and peak cough flow (377 ± 135 vs 492 ± 130 L/min). In CMT1A patients, dMEP and dCMAP were delayed. Patients vs controls showed lower diaphragm excursion (5 ± 2 vs 8 ± 2 cm), diaphragm thickening ratio (DTR, 1.9 [1.6‐2.2] vs 2.5 [2.1‐3.1]), and twPdi (8 ± 6 vs 19 ± 7 cmH₂O; all P < .05). DTR inversely correlated with the CMT‐NSv2 score (r = ?.59, P = .02). There was no group difference in twPgas following abdominal muscle stimulation. Ambulatory CMT1A patients may show phrenic nerve involvement and reduced respiratory muscle strength. Respiratory muscle weakness can be attributed to diaphragm dysfunction alone. It relates to neurological impairment and likely reflects a disease continuum.     

Small and large fiber neuropathy in those with type 1 and type 2 diabetes: a 5‐year follow‐up study

The purpose of this study was to evaluate progression of diabetic polyneuropathy and differences in the spectrum and evolution of large‐ and small‐fiber involvement in patients with diabetes type 1 and 2 over 5 years. Fifty‐nine patients (35 type 1 and 24 type 2) were included. Nerve conduction studies (NCS), quantitative sensory testing, skin biopsy for quantification of intraepidermal nerve fiber density (IENFD), symptom scoring and clinical evaluations were performed. Z‐scores were calculated to adjust for the physiologic effects of age and height/gender. Neuropathic symptoms were not significantly more frequent in type 2 than in type 1 diabetic patients at follow‐up (54% vs. 37%). The overall mean NCS Z‐score remained within the normal range, but there was a small significant decline after 5 years in both groups: type 1 (p = 0.004) and type 2 (p = 0.02). Mean IENFD Z‐scores changed from normal to abnormal in both groups, but only significantly in those with type 2 diabetes (reduction from 7.9 ± 4.8 to 4.3 ± 2.8 fibers/mm, p = 0.006). Cold perception threshold became more abnormal only in those with type 2 diabetes (p = 0.049). There was a minimal progression of large fiber neuropathy in both groups. Reduction of small fibers predominated and progressed more rapidly in those with type 2 diabetes.     

Effect of ischaemia on sensory potentials of normal subjects of different ages

In 73 normal subjects, from 10 to 82 years of age, maximum orthodromic sensory nerve conduction velocity was measured in the median nerve before and during a 30 minute period of vascular occlusion. During ischaemia progressive slowing in conduction velocity, decrease in amplitude, and increase in duration of the sensory action potential evoked at wrist and elbow by supramaximal stimulation of digit III were observed. However, a statistically significant difference (P<0·05 to P<0·01) between subjects was noted by grouping them by age: the older the subject, the longer the persistence of sensory response and the less marked the slowing in conduction velocity. The mechanism of the phenomenon has been discussed in relation to a similar longer resistance to ischaemia found in peripheral nerves of diabetic and uraemic patients.