Meralgia Paresthetica

A muscular construction worker presented with low back pain and lateral left leg pain and numbness. Initially the physicians operated under the assumption the pain was caused by a kidney stone and he was admitted to the medicine service. After his renal CT and lumbar spine MRI were negative, but his pain persisted, neurology was consulted. On exam he had no weakness when full effort was given. His reflexes were normal. His only positive finding was an area of sensation loss consistent with the lateral femoral cutaneous nerve. A pelvic MRI was negative for a compressive lesion. Additional history revealed that he regularly wears a tool belt and he was exerting himself when the pain began. Clinically his syndrome was most consistent with meralgia paresthetica. It is caused by compression injury of the lateral femoral cutaneous nerve, usually as it passes under the inguinal ligament. Treatment includes NSAIDs, rest, and addressing the cause, e.g. obesity, posture, or tool belt. A local anesthetic nerve block can have diagnostic value, but the pain consultants for this patient balked. He was sent home with some improvement in pain and control with oral agents.

Erbay Hakan. Meralgia Paresthetica in Differential Diagnosis of Low-Back Pain. The Clinical Journal of Pain. 18:132-135.

Williams Syndrome

In the July 8 New York Times Sunday Magazine, David Dobbs reviews aspects of Williams Syndrome in "The Gregarious Brain". As others have done, he uses Williams syndrome as a springboard to discuss the genetics of personality, neuroscience, and even the evolution of language.

Williams Syndrome brains are on average 15% smaller than normal. A disproportionate amount of this discrepancy is accounted for by smaller dorsal regions. Ventral regions are denser in synaptic connections. Their affability has in part been linked to their lack of connection between the orbitofrontal cortices and amygdylae when interpreting menacing faces. Therefore they know no social fear.

The link between language and sociability, which Williams seems to demonstrate, provides support for the social-brain theory. It states that human neocortex increased to deal with larger social groups. Across primate species the size of the neocortex correlates with the size of the social group. In this theory language was a neocortical adaptation that allowed the maintenance of a large social network without physical grooming; instead relationships could be cultivated with verbal grooming.

fMRI as Lie Detector

Margaret Talbot takes on fMRI and the history of lie detection in her article "Duped" in the July 2, 2007 New Yorker. One company is touting fMRI as a way to exonerate the innocent and damn the guilty. The number of problems with this modality are numerous. One of the major problems is that sociopaths and hardened criminals have brains that respond to lying differently than normals, i.e. they lack pathways that reinforce remorse and guilt.

Intelligent Design

Not one to pass up flogging a scourge, Richard Dawkins takes on Michael Behe's new book The Edge of Evolution in the New York Times Book Review today. In the review, Dawkins defends science instead of proclaiming atheism or attacking religion. It seems that this is the best way to defend evolution and discount intelligent design: ask where's the evidence and where's the consensus? Dawkins rightly points out that Behe's stand has created a lucrative niche for himself on the speaking circuit. His books have surely found an audience.

Klippel-Feil Anomaly

This condition is a concern to neurologists because the anomaly, congenital fusion of cervical vertebrae, can sometimes have neurologic consequences. The vertebrae aren't actually fused; they fail to segment normally between the third and eighth weeks of development. On examination these patients have short necks, low hairlines, and limitation of neck movement. A recent example had one shoulder lower than the other. The picture in Bradley and Daroff (from where all information is borrowed and adapted) seems to demonstrate the same. Imaging reveals the fused vertebrae. Compression of nerve roots, cervical spinal cord, or vertebral or spinal artery can occur. Interestingly, suspected incomplete decussation of corticospinal fibers can cause mirror movements in children. There are many associated abnormalities, including bifurcated spinal cord. Many patients do just fine. The patient I saw had two discrete transient events characterized as right hand, lower arm, neck and face tingling. Neuroanatomically these events were difficult to ascribe to his K-F anomaly. DWI was negative. There was no history suggestive of an epileptic or migrainous phenomenon.

Music

The author of This Is Your Brain on Music is perfectly poised to write a book about the neuroscience of music. Daniel J Levitin began his career as a musician and sound engineer, and later he passed into academia to better grasp the science behind music’s appeal. His dual interests, music and neuroscience, and their interplay seem to appeal to many others, as evidenced by the book’s ubiquity in like-minded media outlets over the last few months. (Try here.) This likely also reflects the fact that he has written a book comprehensible to those without any music or science training.

The book does not present a cohesive theory for how music is processed in the brain, in part because there isn’t one. Levitin’s fragmentary approach reflects the fragmentary nature of the field. But even the fragments are intriguing. Music first activates the auditory cortex. Then areas adjacent and overlapping with Broca’s interpret musical syntax. Finally the meaning of the music (the musical semantics) is delineated in the mesolimbic system, including regions near Wernicke’s area. This is hardly the whole story. The cerebellum (10% of brain weight; 50-80% of neurons) possesses direct connections from the ear. Through its connections to the basal ganglia it is implicated in rhythm and meter. How all these linkages are coordinated into the experience of music is less clear, but Levitin surely puts many of the pieces on the table.

Levitin introduces a few diseases that offer insights into the neuroscience of music. Those with higher functioning autistism are drawn to the structure of music but they miss the emotional appeal. Perhaps this is a result of their smaller neocerebellums. On the other hand, people with Williams Syndrome have larger neocerebellums and are musically gifted. Levitin casts his net wider still. Citing work done by Schmahmann et al regarding the cerebellar cognitive affective syndromes, he associates socialibility and musicality.

In later chapters, Levitin takes a more psychological approach as he explores the genesis of musical preference and the nature of expertise. In the last chapter he dives into evolutionary psychology. Where this fits into the overarching purpose of the book is not clear. Levitin supports the idea that music, or traits that endow musical ability are present today as a result of sexual selection. Here is not the place to deconstruct each of his arguments for this position. This has been done by many critics of evolutionary psychology. What is more interesting is why intelligent thinkers insist that certain traits exist as the consequence of selection, either sexual or natural. Perhaps the mantle of natural selection bestows prestige and lends credence to an area of research. Regardless, the evolution of music and musical ability as the result of sexual selection is unprovable, and moreover, it does little to advance our understanding of why some music sounds so good.

Chronic Headache

Those unfortunate to suffer from chronic headache present quite a quandary to neurologists. However, the physician can go home without persistent pain in his head. Some of these patients are curable, but many of them will not respond to therapy. This proves as frustrating to the patient as to the doctor.

A Head Case by Michael J. Nelson in the June 10, 2007 New York Times offers a brief account of one patient's (the author's) experience with chronic headache. He tries a number of medications without any relief of the headache that has plagued him for twenty years; he does experience unsettling side effects. In an act of desparation he tries novicaine scalp injections which leave him with worse pain.

This account is matched by many similar experiences of chronic headache patients. Careful, almost algorithmic approaches by enthusiastic headache specialists can yield results, but chronic pain is chronic for a reason.