P-3 vs. TG100-8

Myasthenia Gravis and Local Anesthetics

I have come across a second patient now with MG that exhibited poor analgesia from local anesthetic. A middle-aged female with MG and Hep C underwent external levator repair yesterday. Pain control was poor despite generous amount of subcutaenous infiltration. Paralytic effect was also poor, as orbicular muscle contracted vigorously during unipolar incision. Extra amount of local anesthetic was required, resulting in eventual paralysis of the levator muscle and inablity to assess function of repair on the table. Patient was also exquisitely sensitive to stretching of the levator muscle, even though already immune from pain when muscle pinched by forceps. She is complicated by (1) her hepatic disease which may alter metabolism of lidocaine, and (2) a hyperacute personality which may be equating tactile sensation to pain.

A year ago I performed a cataract phacoemulsification of a 80 year of female with MG. A retrobulbar anesthesia was given due to unsteady eye position pre-op and squeezing of lids. Despite a good RBB, patient regained movement of eye shortly after beginning of case, making rest of procedure more challenging. The procedure was otherwise uncomplicated.

I wonder if MG somehow hinders the efficacy of local anesthetic. A brief PubMed search under "MG and local anesthetic", "MG and lidocaine", and "MG and analgesia" has not turned out report of similiar cases or mechanisms proposed. MG affects the neuromusclar junction via antibody against the nitoctinic ACH receptor. ACh receptor activation normally leads to dipolarization of the muscle cell, involving Voltage-gated Na channels. Lidocaine works by blocking this channels. Therefore one mechanisms of poor akinesia by lidocaine in MG may be a subsequent up-regulation of these Na channels due to chronic ACh receptor suppression. Literature search found only one paper on the subject, which reported DECREASE of Ach and Na channels at the endplate. Marx A, Siara J, Rüdel R Sodium and potassium channels in epithelial cells from thymus glands and thymomas of myasthenia gravis patients.

Association may be complicated as MG comes with other autoimmune conditions. Also, a second type of the MG has been identified that affects MuSK (muscle specific kinnase).

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Gravitational Lensing, Gravitational "Streaking"?

An interesting phenomenon called "gravitation lensing" is caused by a massive object such as a star or a black hole, that intervenes between a distance light source and an observer. This is caused by the bending of light near the gravitational well. Unlike a classical lens which bends light the greatest at the periphery, the gravitation lens bends the light greatest at the center, and weakest at the periphery.





















Thus, instead of a focal point, it has a focal line. And instead of a point image, it produces a ring of light, called the Einstein ring.



























This phenomenon has been used to estimate the size of the intervening object, the "lens", which otherwise cannot be oberved due to lack of native luminance. Here is an animation of the effect of a beam of light moving behind a black hole.


As an ophthalmologist, one would immediately notice the "against" motion of the lens arc, ie, while the light is moving down and to the left, the arc moves in the opposite direction. Imagine the light streaking across comes from a retinoscope, and us the observers are sitting at the back to the retina, i.e. earth, we could conclude that the grativational lens is of plus-power.

While there is no giant hand streaking the distant light source back and forth, the angular motion of the source light relative the lens may be induced either by the motion of the earth, "parallex motion", or of the sun "proper motion". Therefore, it is reasonable to hypothesize that the speed by which the arc migrates may be related to the mass and the relative distances of the lens system. Currently the mass is already able to be calculated by the lens effect, and distance is estimated by red-shift. But this "gravitational streaking" may be useful in aiding their calculations.

PET scan and Sexual Orientation

An article in the July 8th, 08's Proceeding of National Academy of Science boasted this grabbing title: "PET and MRI show differences in cerebral asymmetry and functional connectivity between homo- and heterosexual subjects"

Here's a telling image: Area activated is the amygdalae, the center for pheramon sensing and emotional learning. The study suggests heteralsexual men exhibit unilateral activation, while heteralsexual women exhibit bilateral activation, which is reverved in homosexual men and women.

Jan 4th, Picture(s) of the Da

Ever wonders what c-ANCA and p-ANCA actually look like? Well, I never did either, but here they are.