Is the Fastest MRI a Hologram?

Real‐time MR imaging might exert a profound influence on neuroscience in the future by enabling the direct visualization of neuronal interactions. At this time, however, all practical embodiments of MRI require at least some degree of gradient encoding, and this in turn sets a lower limit of about 100 ms for volume acquisition. A novel formulation of MRI is proposed here which is given the acronym ULTRA (Unlimited Trains of Radio Acquisitions). In the preferred embodiment ULTRA is completely free of gradient reversals, which allows for signal acquisition from the entire object volume simultaneously. This permits a rate of signal acquisition that is increased hundreds of times compared with existing techniques, with full 3‐D imaging in as little as one millisecond. The proposed detector now resembles a holographic recording.     

Is it necessary to use the entire root as a donor when transferring contralateral C_7 nerve to repair median nerve?

If a partial contralateral C_7 nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C_7 nerve is used to repair two nerves, both recipient nerves show good recovery. These findings seem contradictory, as the above two methods use the same donor nerve, only the cutting method of the contralateral C_7 nerve is different. To verify whether this can actually result in different repair effects, we divided rats with right total brachial plexus injury into three groups. In the entire root group, the entire contralateral C_7 root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C_7 root was transected and transferred to the median nerve. In the entire root + posterior division group, the entire contralateral C_7 root was transected but only the posterior division was transferred to the median nerve. After neurectomy, the median nerve was repaired on the affected side in the three groups. At 8, 12, and 16 weeks postoperatively, electrophysiological examination showed that maximum amplitude, latency, muscle tetanic contraction force, and muscle fiber cross-sectional area of the flexor digitorum superficialis muscle were significantly better in the entire root and entire root + posterior division groups than in the posterior division group. No significant difference was found between the entire root and entire root + posterior division groups. Counts of myelinated axons in the median nerve were greater in the entire root group than in the entire root + posterior division group, which were greater than the posterior division group. We conclude that for the same recipient nerve, harvesting of the entire contralateral C_7 root achieved significantly better recovery than partial harvesting, even if only part of the entire root was used for transfer. This result indicates that the entire root should be used as a donor when transferring contralateral C_7 nerve.     

Is the aortic depressor nerve involved in arterial chemoreflexes in rats?

Recent anatomical and physiological studies showed that chemoreceptor afferent fibers are present in the rat aortic depressor nerve (ADN), which has been considered to contain exclusively baroreceptor afferent fibers. However, it remains to be proven whether the chemoreceptor afferents of the ADN are practically involved in chemoreflexes. The present study was performed in chloralose/urethane-anesthetized rats of either Sprague-Dawley (SD) or Wistar strain to examine whether the ADN carries sufficient information regarding arterial hypoxia and hypercapnia, and whether the ADN indeed participates in chemoreflexes, the circulatory and respiratory components. It was found in either strain that afferent discharges of the ADN were not affected at all by hypoxia or hypercapnia, whereas those of the carotid sinus nerve (CSN) markedly increased due to these stimuli. Hypoxia produced hypertension, transient bradycardia followed by tachycardia, and respiratory facilitation, which characterize the chemoreflexes. Any of these responses was not affected at all by the ADN section, but all were abolished by the CSN section. Intraaortic injection of cyanide also induced transient bradycardia and respiratory facilitation, but any of them was not affected by the ADN section while all were abolished by the CSN section. Furthermore, electrical stimulation of the ADN produced solely baroreflex responses, i.e. hypotension and respiratory suppression, whereas that of the CSN provoked chemoreflex responses, i.e. early, transient hypertension and respiratory facilitation. In conclusion, the rat ADN does not contain a functionally significant number of chemoreceptor afferent fibers, if at all, and does not appreciably contribute to generation of chemoreflexes.     

Is the postganglionic sympathetic neuron zinc-enriched? A stop-flow nerve crush study on rat sciatic nerve.

Axonal transport of endogenous zinc ions in the rat sciatic nerve was studied by a stop-flow/nerve crush technique combined with zinc selenide autometallography (ZnSeAMG) at light and electron microscopic levels. Distinct accumulations of ZnSeAMG grains were detected, in particular proximal but also distal to the crushes, 1.5 h after the operation, and the amounts of zinc ions increased further in the following 3-8 h. Ultrastructurally, ZnSeAMG grains were located predominantly in unmyelinated axons. The data suggest that a subpopulation of sciatic nerve axons contains and transports zinc ions both antero- and retrogradely, indicating that the second neuron in the sympathetic nervous system is zinc enriched (ZEN).     

Is carpal tunnel syndrome a slow,chronic, progressive nerve entrapment?

ObjectiveThe aim of this study is to investigate the presenting profile of patients with carpal tunnel syndrome (CTS) at various ages.MethodsWe performed a cross-sectional study of CTS, analysing the correlation between severity and age.ResultsWe examined 3108 subjects with CTS, whose frequency increased from 20.9% for the age group 20–29 years to 61.7% for the age group 50–59 years. It remained at almost 50% in people aged over 80 years (49.2%). More than 50% of people younger than 30 years had mild CTS. Severe CTS progressively increased, reaching more than 50% of the CTS diagnoses in people over 80 years. Of the total number of cases, 80.8% of subjects had bilateral CTS. Mild NCS–EMG abnormalities were seen in 74.1% of patients with unilateral involvement, whereas moderate and severe CTS appeared in 70.3% of patients with bilateral involvement.ConclusionThere was a clear trend of deterioration with advancing years when comparing severity to age.SignificanceCTS seems to be a chronic condition whose signs and symptoms may vary and progress, becoming worse over time.     

Is surgery likely to be successful as a treatment for traumatic lesions of the superficial radial nerve?

In the last 10 years 22 patients with lesions of the superficial branch of the radial nerve have been treated surgically in our neurosurgical department. The patients' main complaints were burning pain and paraesthesia in the region supplied by the superficial branch of the radial nerve. In most cases the lesion was due to tendolysis performed earlier to treat de Quervain tendovaginitis stenosans. In 8 cases external neurolysis was done with conservation of continuity; in 4 cases the nerve was reconstructed after resection of the neuroma (end-to-end-suture or implantation of a vicryl conduit); and in 10 cases the neuroma was resected and transposition of the proximal nerve end was performed. Nineteen patients were available for evaluation of the postoperative results, after an average follow-up of 51 months. Surprisingly, only 5 reported good subjective improvement of pain after surgery. Seven patients reported an unchanged status postoperatively, and in 1 case the pain was even worse after the surgical intervention. Satisfactory results (complete or partial pain relief in 75% of cases) was found to have been achieved in the subgroup of patients treated by resection of the neuroma of the superficial branch of the radial nerve and transposition of the nerve stump. In conclusion, we recommend caution when surgical interventions are considered for traumatic lesions of the superficial radial nerve, because the prospects of success are limited. In addition, we do not consider nerve reconstruction desirable in these circumstances.     

Is the stimulation frequency of the repetitive nerve stimulation test that you choose appropriate?

The repetitive nerve stimulation test (RNST) has been a useful method in the diagnosis of myasthenia gravis (MG). In clinical practice, a short train of repetitive stimulation is usually given at 3 Hz. Although it was documented that lower stimulation frequencies could offer a greater sensitivity, no study has been done to testify the most sensitive stimulation frequency for RNST. To find out an optimal stimulation frequency, we performed RNST at 0.5, 1, 3, 5, 7, 10, 15 and 20 Hz in 15 MG patients and 5 healthy subjects. The results showed that the decremental response was most often seen at 7 Hz rather than at 3 Hz. To augment the sensitivity in the diagnosis of MG, RNST should be performed stimulation not only at 3Hz but also at other frequencies, preferably 7 Hz.     

Ultrasound assessment of sural nerve in Charcot–Marie-Tooth 1A neuropathy

ObjectiveNerve ultrasound (US) has been used to study peripheral nerve disease, and increase of the cross-sectional area (CSA) has been described in demyelinating polyneuropathy. The objective of the current study is to characterise the US features of the sural nerve in a sample of Charcot–Marie-Tooth (CMT) 1A patients.MethodsA total of 20 CMT1A patients were enrolled. As control group we studied 37 age- and sex-matched subjects. All patients underwent clinical examination, neurophysiology and US evaluation of the bilateral sural nerve and right ulnar nerve. US results were correlated with neurophysiology and clinical data.ResultsSural nerve CSA was not increased in the majority of patients (70%), whereas an increased ulnar nerve CSA was present in the whole sample. Inverse relations were found between CSA of the ulnar nerve and body mass index (BMI) (p < 0.0002, R = ?0.8) and CSA of the sural nerve and age (right 0.006, R = ?0.6, left 0.002, R = ?0.6 and left and right p = 0.00003, R = ?0.4).ConclusionsUS showed ulnar CSA enlargement and normal sural nerve CSA.SignificanceThe significance of normal sural nerve CSA in CMT1A patients need to be further investigated, possibly through longitudinal studies.