July 25, 2007


In the July 23, 2007 New Yorker, Oliver Sacks presents the tale of an orthopedic surgeon who demonstrated musicophilia and musicality after being struck by lightning. "A Bolt from the Blue" uses the case of the surgeon to dive into a discussion of the neural basis for out of body experiences and the sudden onset of artistic endeavors.

The article gives evidence for two hypotheses regarding how the unexpected emergence of musical ability may occur. The first involves strengthening of connections between perceptual systems in the temporal lobe and the limbic system. This is achieved by repetitive epileptic activity arising from a temporal focus. The emergence of hypermusia, a gain of function, intuitively seems to fit a hypothesis in which some neural connections, responsible for a certain function, are differentially strengthened. Conversely, and thus counterintuitively, loss of brain tissue, in this article by resection and stroke, has been associated with gain of musical ability. It is the disinhibition of abilities always present but not consciously engaged that is believed to cause this.

When a student taking a jazz class notes that he cannot appreciate rhythm after a temporal lobectomy, the loss of brain tissue mirrors a loss in ability. It is the gain of function after neurologic damage that runs counter to reason, and is therefore far more interesting.

In the past I discussed the case of a woman who became pain-free after a seizure.

July 24, 2007

Post-Hypoxic Movement Disorders

A healthy young male was struck by lightning in the front yard of his home. He developed ventricular fibrillation and was eventually resuscitated. An unclear period of anoxia produced ischemic lesions (DWI - positive) in his basal ganglia bilaterally. He spent an extended period of time in an acute care hospital. Neurology was reinvolved in his care three months after his initial presentation for full body jerks (myoclonus), rigidity, and a persistently open mouth with tongue dyskinesia. These three symptoms had all worsened after his valium was decreased by 50%. His physical exam reveal flexor posturing of the upper extremities with increased tone to the point of rigidity throughout. His hypoxic-ischemic injury has left him without the ability to speak or follow commands. He is able to track consistently with his eyes and move his neck and head toward a stimulus.

This patient's severe disability and seeming movement disorders led to the following paper. Some aspects of it are presented below.

Venkatesan A, Frucht S. Movement Disorders after Resuscitation from Cardiac Arrest. Neurol Clin 24 (2006) 123-132.

After hypoxic-ischemic injury, parkinsonism, dystonia, chorea, tics, athetosis, tremor, and myoclonus have all been described. Post-hypoxic myoclonus (PHM), which can be seen acutely or as a long-term sequela, may be focal, multifocal, or generalized. Acute PHM is characterized by severe, generalized myoclonic jerks in deeply comatose patients. The prognosis associated with acute PHM is extremely poor. The best evidence points to diffuse cortical damage as the cause. Treatment usually consists of IV sedation. Chronic PHM (Lance-Adams Syndrome) is characterized by action myoclonus involving the limbs, stimulus sensitivity, and negative myoclonic jerks. Localization is both cortical and subcortical.

    "It seems that cortical myoclonus is much more common in chronic PHM than subcortical myoclonus, the latter of which tends to cause violent jerks of the proximal limbs and trunk."
First-line treatments are Clonazepam, valproate, and piracetam. Baclofen, diazepam, ethanol, methysergide, GHB, and levetiracetam have also been used.

Of greater importance to this case are the movement disorders caused by damage to the basal ganglia. There seems to be a spectrum of post-hypoxic dystonic and akinetic-rigid syndromes. The akinetic-rigid syndrome developing within three months of the hypoxic event is characterized by "bradykinesia, micrographia, axial and appendicular rigidity, resting or postural tremor, and marked postural instability." Treatment responses are dismal. Those with a dystonic syndrome areyounger than those with a more akinetic-rigid syndrome. Case series suggest that dystonic syndromes predominate in those with putaminal lesions, while the akinetic syndrome occurs in those with pallidal lesions. The mechanism of preferential damage to the basal ganglia has fallen into two camps: the vascular hypothesis which states that there is selective hypoperfusion to the basal ganglia during a hypoxic event; and the metabolic hypothesis which postulates that high metabolic requirements result in selective hypoxic damage.
    "Regardless of the mechanism, it seems that damage to the basal ganglia with preservation of the pyramidal system is a pathologic correlate of delayed posthypoxic dystonia or akinetic-rigid syndromes."

July 18, 2007

Mobius Syndrome

Those with Mobius Syndrome are recognized by their facial diplegia. They lack any facial expression; they have difficulty eating and cannot fully close their eyes. In addition to paresis of CN VII bilaterally, they classically have CN VI pareses. CN V and VIII dysfunction and variable orofacial and limb malformations are also associated with the syndrome.

Since facial diplegia leads to social stigmatization, a surgery has been to developed to correct it. Performed in Toronto at the Hospital for Sick Children, it involves borrowing nerve from the masseter and muscle from the thigh. With practice, according to the website, patients "learn" to involuntarily smile. This has even happened in adults, testament to the plasticity of the human brain at all ages.

The syndrome was identified by the German neurologist Paul Julius Möbius. He should not be confused with August Ferdinand Möbius who independently described the Mobius strip or band. Mobius Band is also a rock group from Brooklyn.

July 16, 2007

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.

July 12, 2007

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.

July 7, 2007

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.

July 1, 2007

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.