The Case Against Spinal Taps

Joab Chapman, MD, PhD, Tel Aviv University, Tel Aviv, Israel, discussed reasons for not performing spinal taps. Among other subjects, he discussed zone electrophoresis and isofunctioning, differential diagnosis of white matter lesions on MRI, and the autoimmune encephalomyelitis-driven hypothesis.

The latest revision of the McDonald Criteria [Polman CH et al. Ann Neurol 2011] does not require CSF analyses to make a diagnosis of MS. This has led to earlier diagnosis with a high degree of specificity and sensitivity [Tintore M et al. Neurology 2003], enabling better counseling and earlier treatment.

Non-invasive imaging methods have become essential for assessing the effects of damage or disease processes [Stroman PW et al. Clin Neurol Neurosurg 2012]. MS is being studied extensively with functional MRI, in both the brain and spinal cord [Filippi M, Rocca MA. Neuroimaging Clin N Am 2009].

MRI may be the most widely used method for detecting pathology in the central nervous system because of its high tissue contrast and relatively high spacial resolution. It also offers several different methods for visualizing tissues and pathology. In addition to detailed anatomical imaging, it allows for angiography as well as diffusion-weighted and functional imaging [Stroman PW et al. Clin Neurol Neurosurg 2012].

MRI techniques may also be useful in the prediction of outcome. Structural techniques, such as diffusion tensor imaging, have been used to associate the structural integrity of white matter tracts with prediction of outcome. Diffusion tensor imaging has also been used to predict recovery following relapse in MS [Freund P et al. Mult Scler 2010].

Advanced MRI techniques image gray matter (GM) lesions in vivo and quantify structural and functional damage of the cortical and subcortical GM [Pirko I et al. Neurology 2007]. Evidence indicates that high and ultra-high field MRI may be useful in imaging nuclei, such as ³¹P, and metabolites, such as glutamate [Srinivasan R et al. Magn Reson Imaging 2009]. This suggests the potential to elucidate the pathological mechanisms of neurodegeneration and disease progression.

High and ultra-high field strength magnets and sophisticated coil technology hold great promise for the development and implementation of techniques with greater sensitivity and specificity to the pathological mechanisms underlying disease processes [Inglese M et al. Mt Sinai J Med 2011].

Consider Other Factors

Florian Deisenhammer, MD, Innsbruck Medical University, Innsbruck, Austria, presented reasons why MRI should not be used for therapeutic decision-making. To make this point, he relied on MRIs from landmark trials (BENEFIT [Kappos L et al. Neurology 2006]; ETOMS [Fillipi M et al. Lancet 2004]; and CHAMPS [Kappos L et al. Neurology 2006])—all double-blind, placebo-controlled, randomized, multicenter trials.

In the BENEFIT trial, researchers examined the effect of treatment on the rate of conversion to CDMS as defined in the Poser criteria [Poser CM et al. Ann Neurol 1983]. They also explored therapeutic effects on the rate of conversion according to a diagnosis of MS as defined by the McDonald Criteria. [McDonald WI et al. Ann Neurol 2001]. These criteria systematically incorporate paraclinical findings, in particular MRI, to increase sensitivity without compromising specificity [Polman CH et al. Ann Neurol 2005; Dalton CM et al. Ann Neurol 2002; Tontore M et al. Neurology 2003]. In the post-hoc analyses of MRI data reading predictability of the therapeutic response according to MRI activity, no common pattern was found. In some studies, patients with high MRI activity responded better while in other studies, the opposite was true (patients with low MRI activity responded better to the treatment). To date, no prospective investigation has looked at the value of MRI for treatment decisions. There is simply not enough good quality data to rely solely on MRI to decide whether individual patients should be put on a particular treatment or should have their treatment changed.

Prof. Deisenhammer discussed further reasons why clinicians should not rely on MRIs by describing a recent neuroloy workshop. Participants, who routinely read scans were simultaneously provided with a series of cases from clinical studies, such as BENEFIT, and study-grade MRIs—highly sophisticated imaging with perfect resolution. The goal of the exercise was for neurologists to judge changes in T2 lesions and to indicate how many they thought they saw.

“This was a very humbling experience for them,” he explained. “The number of lesions identified ranged from none to 30 or 40 new ones. In one instance, there was only one lesion, but the average neurologist saw six. In another case, there were at lest 20 lesions, and the average neurologist saw only two.”

The technology is accurate, but our eyes may be not be, he said, noting the high volume of scans read by radiologists and the small amount of time spent on each one. Under those circumstances, the opportunity for errors in interpretations over time, especially in routine scanning, is great.

Clinicians who make judgments based on the presence of new T2 lesions, need to be very sure that they are actually seeing T2 lesions; this is especially true for small ones.