Neurological and neurosurgical specialties cover a vast range of disorders. In this issue, Maryland Physician explores advances in three very diverse areas of this field in its interviews with three Maryland medical experts: Amiel W. Bethel, M.D, about the re-emergence of total disc replacement in the spine; Bimal G. Rami, M.D., about endonasal pituitary surgery; and Stewart H. Mostofsky, M.D., about new understanding of the motor control issues faced by children with ADHD.
Endonasal Pituitary Surgery
Dr. Rami, co-director (with Marc G. Dubin, M.D., FACS) of the Minimally Invasive Pituitary and Skull Base Center at GBMC, is unapologetically enthusiastic about the advantages of endonasal pituitary surgery to treat micro- and macro-pituitary adenomas. While tumors in this region of the brain are not common, and most are benign, the symptoms they create can greatly impact a patient’s function. The macro adenomas often cause severe double vision and other visual impairments, while the micro adenomas secrete excess hormones, leading to prolactinemia and other endocrine issues.
Until about five years ago, the only approach to tackle tumors in the pituitary fossa was a transnasal or sublabial approach, in which the ENT made an incision in the nose or gum area followed by a destructive approach to the sphenoid sinus. The endonasal procedure, by contrast, uses an exclusively endoscopic approach that, surprisingly, provides superior visualization of the tumor and surrounding anatomy.
“With the endoscope, we can look at the area as if we were right in front of the tumor,” exclaims Dr. Rami. “We employ stereotactic navigation so we know real time where we are in relation to the pre-op CT or MRI. We can perform a more delicate dissection and better preserve the normal surrounding anatomy. Patients benefit by having a shorter hospital stay, far less pain, and often a more complete resection of the tumor than was ever possible using traditional techniques.”
The University of Pittsburgh, where Dr. Rami was trained in the use of the endoscope, pioneered the procedure, which has since been extensively reviewed and validated in the literature over the last five years. “To the best of my knowledge,” he says, “we’re fairly unique in the Baltimore area for employing a purely endoscopic approach, though some surgeons are using a hybrid approach.
“There is a learning curve associated with having to look at the video screen while moving your hands; it’s comparable to playing a video game,” notes Dr. Rami. “But the instruments are largely the same, and the ability to visualize the important structures, such as the carotid arteries and the optic nerves, is extremely advantageous.”
Both the endoscopic and the traditional approach involve collapsing the capsule of the tumor to remove it. However, in the older technique, physicians would sweep out as much of the tissue as possible but depend on post-operative imaging to determine how much of the tumor was removed.
Thanks to the surgeon’s ability to visualize and resect the entire tumor with the endonasal approach, patients typically avoid the serial MRIs that are necessary with partial resections. They also experience fewer symptoms, such as hyper secretions, and are far less likely to need a future craniotomy as a result of a large tumor that wasn’t fully resected.
“We’re performing the procedure on lots of patients who originally underwent the traditional procedure years ago but did not have the entire tumor removed,” Dr. Rami concludes.
Total Disc Replacement (TDR)
The early research on TDRs began in the 60s and 70s, but languished for many decades due to research investigation in the United States. The approach has regained popularity in the last 10 to 15 years, chiefly for cervical degenerative diseases. Amiel Bethel M.D., neurosurgeon at the Baltimore Washington Spine and Neuroscience Center, explains, “Unlike fusion, TDR offers you maintenance of motion at the disc level, while still relieving pain. When you fuse one disc, it negatively affects adjacent discs. TDR is at least as good as spinal fusion for pain relief and function, especially in the cervical area.’
Dr. Bethel comments, “The first FDA-approved devices emerged three to four years ago, with three in current practice and several more in the wings. My group has performed many cervical TDR procedures with excellent outcomes. In our experience, C2-C3 disc replacements do very well.
“When TDR is used on one level, the return to activity is quicker,” he continues. ‘The ideal patient for this procedure is younger and has mild degenerative arthritic changes. It gives us another option and prevents disc degeneration in the future. TDR avoids adjacent disc problems, which affect up to 25% of patients within 10 years.”
Fusion remains the gold standard, especially for patients with more severed spondylosis. New inter-body devices have a lower profile that decreases dysphagia and other common side effects of this procedure.
“Of course, the majority of patients can have their degenerative disc disease treated without surgical intervention,” Dr. Bethel notes. “Patients should be referred to doctors who believe in these alternatives. Care conditioning is very important. I start with treatments such as medication, exercise, PT, chiropractics, yoga, Pilates, acupuncture, physiatry and pain management. About 30% to 40% of patients do well with those treatments. If they fail conservative therapy, we discuss their options. Of course, some patients have severe neurologic symptoms that have progressed to the point where you can almost tell when they come in the door that they’ll need surgery.”
Motor Clues Help Doctors Understand & Predict ADHD Severity
Attention Deficit Hyperactivity Disorder (ADHD), currently the most common child behavioral condition, did not become an official diagnosis until 1980. Practitioners have since primarily focused on the behavioral features of the disorder.
In the late 1970s, early studies identified excessive overflow movements and distractible behavior in children with excessive hyperactive behavior. However, little attention was paid to the motor function effects of ADHD until 2003, when a study observed the presence or absence of overflow movements during walking and other activities, but did not quantify them.
“Despite its prevalence, there is a lack of understanding about the neurobiological basis of ADHD,” says Dr. Mostofsky, M.D, director of the Laboratory for Neurocognitive and Imaging Research at the Kennedy Krieger Institute. “A critical obstacle is the lack of quantitative measures of brain function that would provide a basis for more accurate diagnosis and effective treatment.”
To rectify that situation, Dr. Mostofsky and his colleagues recently published two studies on ADHD that measured the motor control failures associated with excessive impulsivity.
“We and other labs are revisiting motor issues,” says Dr. Mostofsky. “Earlier studies have used blunt measurement approaches to overflow.’
In the first study, children with ADHD performed a finger-tapping task. Any unintentional, overflow movements occurring on the opposite hand were noted. Researchers developed two measurements to quantify the amount of overflow – video recording and electronic goniometers that precisely measure the change in angular displacement across a joint. Children with ADHD showed more than twice the amount of overflow as did typically developing children, with a high degree of correspondence between the results using video and goniometer measurement methods. This was the first time that scientists have been able to quantify the degree to which ADHD is associated with a failure in motor control.
“While we expected to find a strong correlation between ADHD and overflow movements,” notes Dr. Mostofsky, “we were a bit surprised to find that school age boys exhibited far more overflow than girls their age. We think this is age related, since girls mature more quickly.”
In the second study, the researchers investigated inhibitory control in the motor cortex using Transcranial Magnetic Stimulation (TMS) to trigger muscle activity in the hand. Researchers measured the level of muscle activity and monitored the resulting brain activity, and also used a paired-pulse stimulation to measure short interval cortical inhibition (SICI). The degree of cortical inhibition in children with ADHD, measured by SICI, was 40 percent less than typically developing children. Furthermore, within the ADHD group, less motor inhibition correlated with more severe behavioral symptom ratings, as reported by parents.
Dr. Mostofsky explains, “These findings provide a window into identifying relevant biomarkers of ADHD that can be used to improve how we diagnose and treat children with the disorder. Currently, the diagnosis is based chiefly on behavior reports, which is limiting. Further, from a clinical standpoint, it’s helpful to recognize that children with ADHD have difficulty with motor control, which leads to difficulty performing handwriting and other fine motor tasks. Study results such as these may help guide intervention recommendations and accommodations in the school setting. It adds to the growing body of evidence that these are involuntary behaviors, not willful.
“We’ve learned in recent years that the long-term outcomes for children with ADHD are not as good as the general population,” Dr. Mostofsky concludes. “ADHD is associated with higher rates of incarceration, motor vehicle accidents, and other problematic behaviors into adulthood. By identifying physiologic biomarkers, we can improve our ability to more effectively guide specific and targeted interventions, and thereby help improve these long-term outcomes. ”
Bimal G. Rami, M.D., a fellowship-trained neurosurgeon, is co-director of the Minimally Invasive Pituitary and Skull Base Center at GBMC. Dr. Rami also specializes in spinal cord stimulation, disc replacement and neuro-oncology.
Amiel W. Bethel, M.D., a fellowship-trained neurosurgeon with the Baltimore Washington Spine and Neuroscience Center and formerly served as chief of surgery at GBMC. He is also an Assistant Professor in the Department of Neurosurgery at the University of Maryland School of Medicine.
Stewart H. Mostofsky, M.D., is a research scientist and director of the Laboratory for Neurocognitive and Imaging Research at the Kennedy Krieger Institute. He is also an associate professor of neurology at the Johns Hopkins University School of Medicine.