Purpose: Given that the clinical course of oxaliplatin-induced neuropathy is not well defined, the current study was performed to better understand clinical parameters associated with its presentation. Methods: Acute and chronic neuropathy was evaluated in patients receiving adjuvant FOLFOX (fluorouracil, leucovorin, and oxaliplatin) on study N08CB (North Central Cancer Treatment Group, Alliance). Acute neuropathy was assessed by having patients complete daily questionnaires for 6 days with each cycle of FOLFOX. Before each dose of FOLFOX and as long as 18 months after chemotherapy cessation, chronic neurotoxicity was assessed with use of the 20-item, European Organisation for Research and Treatment of Cancer quality-of-life questionnaire for patients with chemotherapy-induced peripheral neuropathy. Results: Three hundred eight (89%) of the 346 patients had at least one symptom of acute neuropathy with the first cycle of FOLFOX; these symptoms included sensitivity to touching cold items (71%), sensitivity to swallowing cold items (71%), throat discomfort (63%), or muscle cramps (42%). Acute symptoms peaked at day 3 and improved, although they did not always resolve completely between treatments. These symptoms were about twice as severe in cycles 2 through 12 as they were in cycle 1. For chronic neurotoxicity, tingling was the most severe symptom, followed by numbness and then pain. During chemotherapy, symptoms in the hands were more prominent than they were in the feet; by 18 months, symptoms were more severe in the feet than they were in the hands. Patients with more severe acute neuropathy during the first cycle of therapy experienced more chronic sensory neurotoxicity (P < .0001). Conclusion: Acute oxaliplatin-induced neuropathy symptoms do not always completely resolve between treatment cycles and are only half as severe on the first cycle as compared with subsequent cycles. There is a correlation between the severities of acute and chronic neuropathies.

Post-surgical neuropathies are usually attributed to mechanical factors, such as compression, stretch, contusion or transection. The role of inflammatory mechanisms in neuropathies occurring after surgeries is poorly appreciated and not well characterized, and may provide a rationale for immunotherapy. A total of 23 selected patients with post-surgical neuropathies received nerve biopsies, of which 21 demonstrated increased inflammation. Here we report the clinical features in these 21 cases of biopsy-confirmed and 12 cases of clinically suspected post-surgical inflammatory neuropathies, in whom no trauma to the nerves was documented. All neuropathies developed within 30 days of a surgical procedure. Of 33 patients, 20 were male and the median age was 65 years (range 24–83). Surgical procedures were orthopaedic (n = 14), abdominal/pelvic (n = 12), thoracic (n = 5) and dental (n = 2). Patients developed focal (n = 12), multifocal (n = 14) or diffuse (n = 7) neuropathies. Focal and multifocal neuropathies typically presented with acute pain and weakness, and focal neuropathies often mimicked mechanical aetiologies. Detailed analyses, including clinical characteristics, electrophysiology, imaging and peripheral nerve pathology, were performed. Electrophysiology showed axonal damage. Magnetic resonance imaging of roots, plexuses and peripheral nerves was performed in 22 patients, and all patients had abnormally increased T₂ nerve signal, with 20 exhibiting mild (n = 7), moderate (n = 12) or severe (n = 1) enlargement. A total of 21 patients had abnormal nerve biopsies that showed increased epineurial perivascular lymphocytic inflammation (nine small, five moderate and seven large), with 15 diagnostic or suggestive of microvasculitis. Evidence of ischaemic nerve injury was seen in 19 biopsies. Seventeen biopsies had increased axonal degeneration suggesting active neuropathy. Seventeen biopsied patients were treated with immunotherapy. In 13 cases with longitudinal follow-up (median 9 months, range 3–71 months), the median neuropathy impairment score improved from 30 to 24 at the time of last evaluation (P = 0.001). In conclusion: (i) not all post-surgical neuropathies are mechanical, and inflammatory mechanisms can be causative, presenting as pain and weakness in a focal, multifocal or diffuse pattern; (ii) these inflammatory neuropathies may be recognized by their spatio-temporal separation from the site and time of surgery and by the characteristic magnetic resonance imaging features; (iii) occasionally post-surgical inflammatory and mechanical neuropathies are difficult to distinguish and nerve biopsy may be required to demonstrate an inflammatory mechanism, which in our cohort often, but not exclusively, exhibited pathological features of microvasculitis and ischaemia; and (iv) recognizing the role of inflammation in these patients’ neuropathy led to rational immunotherapy, which may have resulted in the subsequent improvement of neurological symptoms and impairments.

Action potentials are the end product of synaptic integration, a process influenced by resting and active neuronal membrane properties. Diversity in these properties contributes to specialized mechanisms of synaptic integration and action potential firing, which are likely to be of functional significance within neural circuits. In the hippocampus, the majority of subicular pyramidal neurons fire high-frequency bursts of action potentials, whereas CA1 pyramidal neurons exhibit regular spiking behavior when subjected to direct somatic current injection. Using patch-clamp recordings from morphologically identified neurons in hippocampal slices, we analyzed and compared the resting and active membrane properties of pyramidal neurons in the subiculum and CA1 regions of the hippocampus. In response to direct somatic current injection, three subicular firing types were identified (regular spiking, weak bursting, and strong bursting), while all CA1 neurons were regular spiking. Within subiculum strong bursting neurons were found preferentially further away from the CA1 subregion. Input resistance ( R _N), membrane time constant (τ_m), and depolarizing “sag” in response to hyperpolarizing current pulses were similar in all subicular neurons, while R _N and τ_m were significantly larger in CA1 neurons. The first spike of all subicular neurons exhibited similar action potential properties; CA1 action potentials exhibited faster rising rates, greater amplitudes, and wider half-widths than subicular action potentials. Therefore both the resting and active properties of CA1 pyramidal neurons are distinct from those of subicular neurons, which form a related class of neurons, differing in their propensity to burst. We also found that both regular spiking subicular and CA1 neurons could be transformed into a burst firing mode by application of a low concentration of 4-aminopyridine, suggesting that in both hippocampal subfields, firing properties are regulated by a slowly inactivating, D-type potassium current. The ability of all subicular pyramidal neurons to burst strengthens the notion that they form a single neuronal class, sharing a burst generating mechanism that is stronger in some cells than others.