The pathophysiological role of endoneurial inflammatory edema in early classical Guillain-Barré syndrome

The objective of this review was to analyze the pathophysiological role of endoneurial inflammatory edema in initial stages of classic Guillain-Barré syndrome (GBS), arbitrarily divided into very early GBS (≤ 4 days after symptom onset) and early GBS (≤ 10 days). Classic GBS, with variable degree of flaccid and areflexic tetraparesis, encompasses demyelinating and axonal forms. Initial autopsy studies in early GBS have demonstrated that endoneurial inflammatory edema of proximal nerve trunks, particularly spinal nerves, is the outstanding lesion. Variable permeability of the blood-nerve barrier dictates such lesion topography. In proximal nerve trunks possessing epi-perineurium, edema may increase the endoneurial fluid pressure causing ischemic changes. Critical analysis the first pathological description of the axonal form GBS shows a combination of axonal degeneration and demyelination in spinal roots, and pure Wallerian-like degeneration in peripheral nerve trunks. This case might be reclassified as demyelinating GBS with secondary axonal degeneration. Both in acute motor axonal neuropathy and acute motor-sensory axonal neuropathy, Wallerian-like degeneration of motor fibers predominates in the distal part of ventral spinal roots abutting the dura mater, another feature re-emphasizing the pathogenic relevance of this area. Electrophysiological and imaging studies also point to a predominant alteration at the spinal nerve level, which is a hotspot in any early GBS subtype. Serum biomarkers of axonal damage, including neurofilament light chain and peripherin, are increased in the great majority of patients with any early GBS subtype; endoneurial ischemia of proximal nerve trunks could contribute to such axonal damage. It is concluded that inflammatory edema of proximal nerve trunks is an essential pathogenic event in early GBS, which has a tangible impact for accurate approach to the disease.

Assessing the upper motor neuron in amyotrophic lateral sclerosis using the triple stimulation technique: A multicenter prospective study

OBJECTIVE

To evaluate the relevance of transcranial magnetic stimulation (TMS) using triple stimulation technique (TST) to assess corticospinal function in amyotrophic lateral sclerosis (ALS) in a large-scale multicenter study.

METHODS

Six ALS centers performed TST and conventional TMS in upper limbs in 98 ALS patients during their first visit to the center. Clinical evaluation of patients included the revised ALS Functional Rating Scale (ALSFRS-R) and upper motor neuron (UMN) score.

RESULTS

TST amplitude ratio was decreased in 62% of patients whereas conventional TMS amplitude ratio was decreased in 25% of patients and central motor conduction time was increased in 16% of patients. TST amplitude ratio was correlated with ALSFRS-R and UMN score. TST amplitude ratio results were not different between the centers.

CONCLUSIONS

TST is a TMS technique applicable in daily clinical practice in ALS centers for the detection of UMN dysfunction, more sensitive than conventional TMS and related to the clinical condition of the patients.

SIGNIFICANCE

This multicenter study shows that TST can be a routine clinical tool to evaluate UMN dysfunction at the diagnostic assessment of ALS patients.

Repeater F-waves in amyotrophic lateral sclerosis: Electrophysiologic indicators of upper or lower motor neuron involvement?

OBJECTIVE

To extract insight about the mechanism of repeater F-waves (Frep) by exploring their correlation with electrophysiologic markers of upper and lower motor neuron dysfunction in amyotrophic lateral sclerosis (ALS).

METHODS

The correlations of Frep parameters with clinical scores and the results of neurophysiological index (NI), MScanfit MUNE, F/M amplitude ratio (F/M%), single and paired-pulse transcranial magnetic stimulation (TMS), and triple stimulation technique (TST) studies, recorded from abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles of 35 patients with ALS were investigated.

RESULTS

Frep parameters were correlated with NI and MScanfit MUNE in ADM muscle and F/M% in both muscles. None of the Frep parameters were correlated with clinical scores or TST and TMS measures. While the CMAP amplitudes were similar in the two recording muscles, there was a more pronounced decrease of F-wave persistence in APB, probably heralding the subsequent split hand phenomenon.

CONCLUSION

Our findings suggest that the presence and density of Freps are primarily related to the degree of lower motor neuron loss and show no correlation with any of the relatively extensive set of parameters for upper motor neuron dysfunction.

SIGNIFICANCE

Freps are primarily related to lower motor neuron loss in ALS.

Is the triple stimulation technique a better quantification tool of motor dysfunction than motor evoked potentials in multiple sclerosis?

The triple stimulation technique (TST) was rarely used in multiple sclerosis (MS). This study aimed to compare TST and motor evoked potentials (MEP) for the quantification of motor dysfunction. Central motor conduction based on MEP (four limbs) and TST (upper limbs) was assessed in 28 MS patients with a median Expanded Disability Status Scale (EDSS) of 4. EDSS, timed 25-foot walk (T25FW), grasping strength and motor components of the MS functional composite were evaluated. Regression analysis was used to assess the relationship between MEP, TST and clinical findings. TST was negatively correlated with EDSS (r = - 0.74, p < 0.0001) and to a lesser extent with T25FW (r = - 0.47, p < 0.05), and grasping strength (r = - 0.43, p < 0.05). A multiple regression analysis underlined the better correlation between clinical data and TST (R² = 0.56, p < 0.0005) than with MEP (0.03 < R² < 0.22, p > 0.05). This study evidenced the value of TST as a quantification tool of motor dysfunction. TST appeared to reflect a global disability since it was correlated not only to hand function but also to walking capacity.

Diagnosing chronic inflammatory demyelinating polyradiculoneuropathy with triple stimulation technique

OBJECTIVE

To assess the value of triple stimulation technique (TST) for diagnose of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

METHODS

Seven clinically suspected CIDP patients who did not fulfill EFNS/PNS electrodiagnostic criteria for demyelinating neuropathy were enrolled in our study. Routine nerve conduction studies, lumbar puncture, spinal cord magnetic resonance imaging and TST were detected. The patients were being treated with oral prednisone starting at 1 mg/kg daily. The overall disability sum score was performed to evaluate the effect of corticosteroids.

RESULTS

Twenty-eight motor nerves were tested with TST, two conduction blocks (CBs) were detected between the root emergence and the Erb point in six patients respectively and one CB was detected in one patient. Symptoms of all seven patients improved after treatment with oral prednisone.

CONCLUSION

TST can detect CBs located between the root emergence and the Erb point. TST is useful for early diagnosis of CIDP.