Clinical Manifestations of Isolated Elevated Homocysteine-Induced Peripheral Neuropathy in Adults

Clinical feature and sural biopsy study in nitrous oxide-induced peripheral neuropathy

Objective

The objective was to analyze the clinical characteristics and pathological characteristics of sural biopsy in nitrous oxide (N₂O) -induced peripheral neuropathy.

Methods

We recruited 18 patients with N₂O abuse-induced neurological disorders and reported their demographic data, clinical manifestations, laboratory examinations, and nerve conduction studies. Seven patients underwent sural nerve biopsy pathologic examination.

Results

All 18 patients had polyneuropathy, the nerve conduction results showed significant reductions in motor and sensory amplitudes, slowing of conduction velocities, and prolongation of latencies in most tested nerves compared to the controls. Toluidine blue staining of semi-thin sections of sural nerve biopsy showed decreased myelinated nerve fiber density, increased thin myelinated nerve fiber density, and axonal regeneration. Electron microscopy showed axonal degeneration and nerve regeneration.

Conclusion

The main manifestations of peripheral nerve damage caused by the abuse of N₂O are lower limb weakness and distal sensory disorder. The nerve conduction study results demonstrated that mixed axonal and demyelinating neuropathy was the most common type of neuropathy. Sural biopsy showed the main pathological change was chronic axonal degeneration.

Tolcapone improves outcomes in patients with Parkinson disease treated by levodopa/carbidopa intestinal gel: A pilot study

BACKGROUND

Patients with Parkinson disease (PD) treated with levodopa/carbidopa intestinal gel (LCIG) have higher prevalence of hyperhomocysteinemia and peripheral nerves damage.

OBJECTIVE

The aim of our study was to test the effect of catechol-O-methyl transferase inhibitor tolcapone-as an add-on therapy to LCIG in patients with PD-on homocysteine (HCY) metabolism and nerve conduction study (NCS) parameters.

METHODS

We evaluated NCS and serum B12, folic acid, and homocysteine in 16 patients with advanced PD on LCIG. Quality of life (QoL) was also assessed. Six subjects were treated with tolcapone add-on therapy (and LCIG dose reduction), 5 with B vitamin supplementation, and 5 without additional treatment.

RESULTS

The level of HCY increased among patients without treatment (4.95 ± 12.54), and decreased in the vitamin (-17.73 ± 11.82) and tolcapone groups (-8.81 ± 8.36). Patients with tolcapone demonstrated improvement in polyneuropathic symptoms and signs compared with patients treated with vitamins or those without additional treatment (-0.83, d = 0.961). Although the most robust improvement in NCS parameters were observed with tolcapone, the findings were inconsistent to prove the effect of any intervention. Only tolcapone treatment was associated with improvement in QoL (d = 1.089).

CONCLUSION

Our study indicates potential of tolcapone add-on therapy in LCIG treated patients in control of homocysteine levels, and improvement of polyneuropathic symptoms, as well as QoL.

Fiber selectivity of peripheral neuropathy in patients with Parkinson's disease

OBJECTIVE

To determine the function of each type of peripheral nerve fiber and investigate the possible role of levodopa (LD) in peripheral neuropathy (PN) in Parkinson's disease (PD) patients.

METHODS

We enrolled 60 patients with idiopathic PD. All PD patients were divided into three groups: levodopa exposure >3 years (LELD), levodopa exposure ≤3 years (SELD) and de novo patients with PD (NOLD). The current perception threshold (CPT), which was measured by Neurometer at 2000, 250 and 5 Hz, the level of homocysteine, Vitamin B12 and folic acid in plasma, were compared with those of sex- and age-matched healthy controls (HCs).

RESULTS

Current perception threshold was higher at 250 Hz (p < .05) and 5 Hz (p < .05) in the LELD group than the NOLD, SELD, and control group. CPT was lower at 5 Hz in the NOLD than in the HCs group (p < .05). The CPT of the more affected side of PD patients was positively correlated with H-Y stage at 5 Hz current stimulation (r = .42, p = .01). Multivariate logistic regression analysis showed that elevated homocysteine levels were the risk factor of sensory nerve injury in PD patients (p < .01). Serum homocysteine levels were positively correlated with levodopa (LD) daily dose, LD equivalent daily dose, and LD cumulative lifetime dose (p < .05).

CONCLUSIONS

Peripheral neuropathy in PD patients can occur in the early stage of PD exhibiting as hyperesthesia and is fiber selectivity, especially for Aδ and C nerve fibers. PN in PD patients is related to PD itself and long-term LD exposure. Elevated plasma homocysteine is a risk factor for PN in PD patients.

Myeloneuropathy induced by recreational nitrous oxide use with variable exposure levels

BACKGROUND

Although several case series have described nitrous oxide-associated neurological disorders, a comprehensive assessment of exposure characteristics (e.g., time to onset, level of exposure) in substance abusers has not been performed. The aim of this study was to describe the onset patterns of recreational use of nitrous oxide-induced neurological disorders.

METHODS

All cases of neurological disorders related to nitrous oxide recreational use reported to the Hauts-de-France addictovigilance center between January 2019 and August 2020 were selected. Only cases requiring hospitalization with informative data to perform the nitrous oxide causality assessment were included.

RESULTS

A total of 20 cases from 5 hospitals were included. The male-to-female ratio was 6:1 and the median age was 19 years (range 16-34). The neurological presentation [myeloneuropathy 64% (7/11), sensorimotor neuropathy 36% (4/11)] included for all patients gait disorders due to proprioceptive ataxia and limb hypoesthesia. The median dose used per occasion was 100 cartridges (range 5-960; n=19). The median time from the start of nitrous oxide use to the onset of neurological symptoms was 6 months (range 0.7-54; n=16). The cumulative dose was significantly higher in patients with damage to all four limbs than in patients with lower limbs symptoms only (p=0.042).

CONCLUSIONS

A low intermittent exposure may be sufficient to cause neurological damage in some subjects, suggesting that, at the population level, there is no safe exposure to nitrous oxide in recreational settings. The severity of neurological impairment could increase once used at high doses and for prolonged durations of nitrous oxide.

SPECT findings on neuropsychiatric symptoms caused by nitrous oxide abuse

OBJECTIVE

The aim of the study was to investigate the clinical, neuropsychological, and regional cerebral blood flow (rCBF) perfusion changes in patients with neuropsychiatric symptoms caused by nitrous oxide (N₂O) abuse.

METHODS

A total of 16 patients with neuropsychiatric symptoms caused by nitrous oxide abuse were recruited for this study. The study was carried out in the withdrawal phase of N₂O abuse. A 925-1110 MBq ^99mTc-ECD was administered intravenously. SPECT/CT images were collected with a low-energy and high-resolution collimator. The region uptake statistics of different brain regions of interest between patients with N₂O abuse and normal people of the databases for younger subjects from the Scenium DB Comparison software were calculated automatically.

RESULTS

The clinical manifestations of the 16 patients with neuropsychiatric symptoms were mood lability, anxiety, hallucination, delusion, agitation, confusion, and other psychiatric symptoms. In addition, 15 of the patients also complained of memory decline; 14 patients manifested numbness or paresthesia; 14 patients developed limb weakness, and their motor impairments were more severe in the lower limbs than in the upper limbs; and eight patients had urinary and defecation disturbances. In the neuropsychological examination, the BPRS score was 54.69 ± 11.48, the HAMD score was 30.00 ± 11.06, the HAMA score was 18.06 ± 5.77, the MMSE score was 28.06 ± 2.29, and the MoCA score was 25.06 ± 3.40. SPECT showed hypoperfusion in the frontal and temporal lobes, which is consistent with the clinical findings.

CONCLUSION

This was the first study to demonstrate the obvious effect of N₂O abuse on CBF in patients with neuropsychiatric symptoms. CBF perfusion imaging is helpful to detect the changes in the local brain functional activity in patients with N₂O abuse.

The Prognostic Value of Homocysteine in Acute Ischemic Stroke Patients: A Systematic Review and Meta-Analysis

Background: This comprehensive meta-analysis aimed to assess whether an increased homocysteine (Hcy) level is an independent predictor of unfavorable outcomes in acute ischemic stroke (AIS) patients.

Methods: A comprehensive literature search was conducted up to August 1, 2020 to collect studies reporting Hcy levels in AIS patients. We analyzed all the data using Review Manager 5.3 software.

Results: Seventeen studies with 15,636 AIS patients were selected for evaluation. A higher Hcy level was associated with a poorer survival outcome (OR 1.43, 95% CI: 1.25–1.63). Compared with the AIS group, Hcy levels were significantly lower in the healthy control patients, with an SMD of 5.11 and 95% CI (1.87–8.35). Analysis of the different subgroups of AIS demonstrated significant associations between high Hcy levels and survival outcomes only in Caucasian and Asian patients. Moreover, whereas high Hcy levels were closely associated with gender, B12 deficiency, smoking, and patients who received tissue plasminogen activator treatment, no significant difference was found between increased Hcy levels and age, drinking, hypertension, diabetes mellitus, and hyperlipidemia. In addition, the cut-off value (20.0 μmol/L) might be an optimum cut-off index for AIS patients in clinical practice.

Conclusion: This meta-analysis reveals that the Hcy level may serve as an independent predictor for unfavorable survival outcomes in AIS patients, particularly in Caucasian and Asian AIS patients. Further studies can be conducted to clarify this relationship.

Peripheral Nervous System Involvement in Late-Onset Cobalamin C Disease?

Background: Cobalamin C (cblC) has a fundamental role in both central and peripheral nervous system function at any age. Neurologic manifestations may be the earliest and often the only manifestation of hereditary or acquired cblC defect. Peripheral neuropathy remains a classical but underdiagnosed complication of cblC defect, especially in late-onset cblC disease caused by mutations in the methylmalonic aciduria type C and homocysteinemia (MMACHC) gene. So the clinical, electrophysiological, and pathological characteristics of late-onset cblC disease are not well-known.

Methods: A retrospective study of patients with late-onset cblC disease was conducted at our hospital on a 3-year period. The neuropathy was confirmed by the nerve conduction study. Sural biopsies were performed in 2 patients.

Results: Eight patients were identified, with a mean onset age of 16.25 ± 6.07 years. All patients had methylmalonic aciduria, homocysteinemia, compound heterozygous MMACHC gene mutations were detected in all patients, and 7/8 patients with c.482G>A mutation. One patient concomitant with homozygote c.665C>T mutation in 5,10-methylenetetrahydrofolate reductase (MTHFR) gene. All patients showed limb weakness and cognitive impairment. Five patients had possible sensorimotor axonal polyneuropathy predominantly in the distal lower limbs. Sural biopsies showed loss of myelinated and unmyelinated fibers. Electro microscopy revealed crystalline-like inclusions bodies in Schwann cells and axonal degeneration.

Conclusion: Late-onset cblC disease had possible heterogeneous group of distal axonal neuropathy. c.482G>A mutation is a hot spot mutation in late-onset cblC disease.

Clinical and electrodiagnostic characteristics of nitrous oxide-induced neuropathy in Taiwan

OBJECTIVE

Nitrous oxide-induced neuropathy is toxic neuropathy occasionally encountered in Taiwanese neurological clinics. Only several case reports described their electrodiagnostic features. We used a case-control design to investigate the detailed electrodiagnostic characteristics and possible factors relating to severe nerve injury.

METHODS

We retrospectively reviewed 33 patients with nitrous oxide-induced neuropathy over a 10-year period and reported their demographic data, spinal cord MRI, laboratory examinations and nerve conduction studies. 56 healthy controls' nerve conduction studies were collected for comparison analysis.

RESULTS

We noted significant motor and sensory amplitudes reduction, conduction velocities slowing, and latencies prolongation in most tested nerves compared to the controls. Similar nerve conduction study characteristics with prominent lower limbs' motor and sensory amplitudes reduction was observed in patient groups with or without abnormal vitamin B12 and/or homocysteine levels. Among those with lower limbs' motor or sensory amplitudes reduction <20% of the lower limit of normal, higher homocysteine levels were detected.

CONCLUSIONS

Severe impairments of the lower limbs' sensory and motor amplitudes were frequently noted in patients with nitrous oxide exposure. Nitrous oxide exposure itself is an important factor for the development of neuropathy.

SIGNIFICANCE

Our study contributes to the understanding of electrodiagnostic features underlying the nitrous oxide-induced neuropathy.