An electrophysiological approach to the diagnosis of neurogenic dysphagia: implications for botulinum toxin treatment

OBJECTIVES

Botulinum toxin (BTX) injection into the cricopharyngeal (CP) muscle has been proposed for the treatment of neurogenic dysphagia due to CP hyperactivity. The aim was to determine whether an electrophysiological method exploring oropharyngeal swallowing could guide treatment and discriminate responders from non-responders, based on the association of CP dysfunction with other electrophysiological abnormalities of swallowing.

METHODS

Patients with different neurological disorders were examined: Parkinson disease, progressive supranuclear palsy, multiple system atrophy-Parkinson variant, multiple system atrophy cerebellar variant, stroke, multiple sclerosis and ataxia telangiectasia. All patients presented with clinical dysphagia, and with complete absence of CP muscle inhibition during the hypopharyngeal phase of swallowing. Each patient underwent clinical and electrophysiological investigations before and after treatment with BTX into the CP muscle of one side (15 units of Botox). Clinical and electrophysiological procedures were performed in a blind manner by two different investigators. The following electrophysiological measures were analysed: (1) duration of EMG activity of suprahyoid/submental muscles (SHEMG-D); (2) duration of laryngopharyngeal mechanogram (LPM-D); (3) duration of the inhibition of the CP muscle EMG activity (CPEMG-ID); and (4) interval between onset of EMG activity of suprahyoid/submental muscles and onset of laryngopharyngeal mechanogram (I-SHEMG-LPM).

RESULTS

Two months after treatment, 50% of patients showed a significant improvement. Patients with prolonged or reduced SHEMG-D values and prolonged I-SHEMG-LPM values did not respond to BTX. Therefore, values for which BTX had no effect (warning values) were identified.

CONCLUSIONS

This electrophysiological method can recognise swallowing abnormalities which may affect the outcome of the therapeutic approach to dysphagia with BTX treatment.

Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes

OBJECTIVES

To assess the presence, severity, and differences in dysphagia in Parkinson disease (PD), Parkinson variant of multiple system atrophy (MSA-P), and progressive supranuclear palsy (PSP), and to study the pathophysiology of swallowing abnormalities in these disorders.

METHODS

We applied an electrophysiologic method to evaluate oral-pharyngeal swallowing. We analyzed the following measures: duration of EMG activity of suprahyoid/submental muscles (SHEMG-D); duration of laryngeal-pharyngeal mechanogram (LPM-D); duration of the inhibition of the cricopharyngeal muscle activity (CPEMG-ID); interval between onset of EMG activity of suprahyoid/submental muscles and onset of laryngeal-pharyngeal mechanogram (I-SHEMG-LPM); and swallowing reaction time (SRT).

RESULTS

The prolongation of I-SHEMG-LPM was more typical in PD, whereas the most distinctive finding both in patients with PSP and MSA-P was the reduction or the absence of CPEMG-ID early in the course of the disease.

CONCLUSIONS

Involvement of the peduncolo-pontine tegmental nucleus, with subsequent dysfunction of basal ganglia and of the medullary central pattern generator of swallowing, may account for the abnormalities detected in these parkinsonian syndromes. The method described was able to identify swallowing abnormalities also in patients without symptoms of dysphagia and to evaluate dysphagia severity in all patients.

Proximal nerve conduction by high-voltage electrical stimulation in S1 radiculopathies and acquired demyelinating neuropathies

OBJECTIVE

To evaluate the reliability and sensitivity of the high-voltage electrical stimulation for studying proximal conduction of peripheral motor axons in normal subjects, S(1) radiculopathies and acquired demyelinating neuropathies.

METHODS

Twelve patients with compressive S(1) radiculopathy, 22 patients with acquired demyelinating neuropathy and 29 healthy volunteers were examined. The conduction of peripheral motor axons between lumbosacral roots and the sciatic nerve at the gluteal fold was investigated by high-voltage electrical stimulation delivered percutaneously.

RESULTS

The main electrophysiological finding in S(1) radiculopathy was an abnormal side to side difference in the amplitude of the compound motor action potential by proximal stimulation. Overall, the frequency of abnormalities detected by using high-voltage electrical stimulation was similar to that found with conventional EMG studies, and the two methods showed electrophysiological alterations in the same patients. In all patients with acquired demyelinating neuropathy, the proximal motor nerve conduction velocity from lumbosacral roots to the sciatic nerve at the gluteal fold was reduced; proximal stimulation of the motor axons revealed electrophysiological abnormalities more often than when using other electrophysiological techniques (F wave and H reflex).

CONCLUSIONS

High-voltage electrical stimulation of peripheral motor axons shows high sensitivity in detecting proximal neuropathies; it can also define the site and relevance of proximal lesions in the peripheral nervous system better than other conventional techniques.

Hemoglobin near-infrared spectroscopy and surface EMG study in muscle ischaemia and fatiguing isometric contraction

BACKGROUND

To assess how muscle ischaemia and isometric fatiguing contraction influence oxygen content in striated muscle.

METHODS

We simultaneously measured changes in hemoglobin near-infrared (NIR) spectroscopy and in surface EMG before, during, and after muscle ischaemia and ischaemia plus muscle isometric fatiguing contraction. Seventeen healthy male subjects (age range: 19-40 yrs) were examined in our Clinical Neurophysiology Unit. Test I (9 subjects): hemoglobin NIR spectroscopy and stimulated surface EMG were measured for 2 minutes at rest, for 4 minutes during complete ischaemia of tibialis anterior muscle, and for twelve minutes during recovery. Test II (all subjects): hemoglobin NIR spectroscopy and surface EMG were measured for 2 minutes with the subjects performing brief non-fatiguing contractions, for 4 minutes with the subject performing maximal isometric contraction in complete ischaemia, and for twelve minutes during recovery. EMG parameters measured: median density frequency (MDF); muscle fiber conduction velocity (MFCV). NIR spectroscopy parameters measured: percentage of amplitude decrement (% AD) and nadir time (NT) during ischaemia and ischaemic effort; half-recovery time (1/2 RT) from ischaemia effort.

RESULTS

At EMG, we observed a significant shift towards lower values of both MFCV and MDF during fatiguing isometric contraction. MDF recovery was faster then MFCV recovery. At NIR spectroscopy, the 1/2 RT slowed a fast pattern in twelve subjects and a slow pattern in five. A significant relationship was found between AD% and 1/2 RT values of test I and AD% and 1/2 values of test II. We found a positive relationship between NT and 1/2 RT in test II.

CONCLUSIONS

Surface EMG and hemoglobin NIR spectroscopy can be applied simultaneously to evaluate both fatigue intensity and blood flow changes in striated muscle.

Electrophysiologic study of central motor pathways in ataxia-telangiectasia

To date, corticospinal tract functional integrity in ataxia-telangiectasia has not been studied. Thorough evaluation of central motor pathways is also lacking in neuropathologic and clinical studies. Using electromagnetic stimulation, we assessed the integrity of the corticospinal tracts in eight patients with ataxia-telangiectasia. Cortical and peripheral compound motor action potentials were recorded from the abductor pollicis brevis muscle. Recordings of the shortest F-wave latency and of the compound motor action potential distal latency were made from the abductor pollicis brevis muscle after electrical stimulation of the median nerve at the wrist. A significant increase in central motor conduction time was observed in four patients, two of whom had clinical findings compatible with a pyramidal lesion. This study demonstrates involvement of the central motor pathways in ataxia-telangiectasia, which appears to be more frequent late in the course of the disease.