Central pontine myelinolysis is a rare neurologic disorder that is defined by demyelination of longitudinally descending tracts and transversly crossing fibers in the basis pontis. Frequently observed clinical manifestations of this disorder include sudden weakness, dysphagia, loss of consciouness and locked-in syndrome. However, there have been a few studies that reported a benign course of this disease, which include cerebellar signs, such as ataxia, intention tremor, and dysarthria. Here we report on a 53-year-old male with a history of liver cirrhosis who showed the cerebellar type of central pontine myelinolysis. The patient was diagnosed with central pontine myelinolysis based on clinical presentations and magnetic resonance imaging findings after a liver transplantation. Conventional magenetic resonance imaging (MRI) revealed the preservation of the corticospinal tract and abnormal pontocerebellar fibers. However, these findings were not sufficient to define the pathophysiology of our patient. Electrophysiologic analysis and diffusion tensor imaging (DTI) were performed to investigate cerebellar signs in this case. Delayed central motor conduction time (CMCT) to the tibialis anterior muscle with transcranial magnetic stimulation (TMS) was observed, which indicated demyelination of the corticospinal tract. Also, diffusion tensor imaging showed abnormal pontocerebellar fibers, which might have been caused by cerebellar dysfunction in our patient. A combination of TMS and DTI was also used to determine the pathophysiology of this disease.
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Many factors have been identified which to affect the rate of propagation of impulses along motor fibers. These include temperature changes around the nerve, diameter of the axon, degree of myelinization, age of infants, and local environment of the nerve. Motor nerve conduction velocity and Hoffman's reflex latency have been used to assess the degree of myelination and maturation of the nervous system. The conduction velocities in infants of a short gestational age are significantly lower than those of the fullterm infants. The extrauterine myelination and maturation might increase nerve conduction velocity. We measure the median motor nerve conduction velocity, compound muscle action potentials amplitude and H-reflex latency of premature infants to determine the neurological maturation after birth. The premature infants with gestational age above 37 weeks have a significantly higher conduction velocity and a shorter H-reflex latency than those of gestational age below 37 weeks. The premature infants with weight over 2.5 kg have a significantly higher conduction velocity, larger compound muscle action potentials amplitude and a shorter H-reflex latency than those of weight below 2.5 kg. And there is a statistically significant negative correlation of the H-reflex latency with the postmenstrual age. The determination of motor nerve conduction velocities and H-reflex latencies seem to be an additional method in assessing the degree of maturity in infants after birth.
Objective: To assess the facial and trigeminal nerve involvement in diabetic patients using blink reflex study and direct facial motor conduction study.
Method: The subjects were 397 diabetic patients and 34 normal controls. Diabetic patients were subdivided into two groups based on the findings of nerve conduction studies of limb nerves.: Group I, patients with diabetic polyneuropathy; Group II, patients without diabetic polyneuropathy. The blink reflexes and direct facial motor responses and R1 latency/direct response latency (R/D) ratio were obtained in all the subjects. R1 latency was correlated to the findings of nerve conduction studies of limb nerves.
Results: 1) R1 latencies or R2 latencies were abnormally prolonged in 22.4% of Group I, 3.3% of Group II, and direct facial responses were abnormal in 11.8% of Group I, 2% of Group II. 2) There were no significant differences in R/D ratio between the two groups. 3) These findings suggest that not only the facial nerve, but also the trigeminal nerve or brain stem could be affected in diabetic patients with polyneuropathy.
Conclusion: In diabetic patients, blink reflex can provide useful information in determining the degree and distribution of cranial nerve and brain stem lesions.
Objective: To investigate the anatomy of the ulnar nerve according to the degree of elbow flexion and to obtain optimal elbow position for ulnar nerve conduction study.
Methods: Eleven elbows in nine cadavers were dissected. We estimated the 10 cm elbow segment to be the distance between 2 points, 4 cm distal and 6 cm proximal to the center of the cubital tunnel, which was determined to be the halfway point between the medial epicondyle and olecranon with elbow position in extension and 45o, 90o, 135o flexion. Anatomical measurements of the actual length of ulnar nerve, distance between medial epicondyle and ulnar nerve, and distance between medial epicondyle and olecranon were obtained in each position. The actual length of the ulnar nerve was measured between two points of the ulnar nerve closest to the landmarks of the estimated 10 cm with flexible ligature.
Results: The actual lengths of ulnar nerve were 10.23 cm, 10.00 cm, 9.44 cm, and 9.08 cm in elbow extension, and 45o, 90o, 135o flexion, respectively. The difference between actual length and estimated lengths were least in 45o elbow flexion (p=0.0001). The distance between medial epicondyle and olecranon increased with increasing elbow flexion (p=0.0001). However, there was no difference in the distance between medial epicondyle and ulnar regardless of the elbow position. As a result, the ulnar nerve seemed to have migrated anteriorly in the cubital tunnel with increasing elbow flexion.
Conclusion: This study suggest that the optimal angle in ulnar nerve conduction study would be 45o flexion, under the condition that the distance measurement is through the halfway point between the medial epicondyle and olecranon.
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