Role of DAT-SPECT in diagnostic work-up of Parkinsonism

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Role of DAT-SPECT in diagnostic work-up of Parkinsonism Powered By Docstoc
					774                                                   LETTERS TO THE EDITOR

                                             Masato Kanazawa, MD       2. The authors suggest that combining [123I]FP-CIT with
                                           Department of Neurology        postsynaptic imaging using [123I]iodobenzamide (IBZM)
                                            Brain Research Institute      can support the diagnosis of progressive supranuclear palsy.
                                                 Niigata University       In our series, we also looked into this and found that this
                                                     Niigata, Japan       combination, although used in routine practice, is of little
                                                                          use in diagnostically delineating IPD from the atypical par-
                                   Takayoshi Shimohata, MD, PhD           kinsonism syndromes.2 Our literature analysis yielded sim-
                                         Department of Neurology          ilar results.3
                                          Brain Research Institute     3. The authors conclude that DAT-SPECT can provide valu-
                                                Niigata University        able additional information in patients with inconclusive
                                                   Niigata, Japan         parkinsonian symptoms, particularly early in the disease.
                                                                          This is exactly the point, as this is the situation in which the
                                  Masatoyo Nishizawa, MD, PhD*            neurologist needs an additional diagnostic tool above the
                                         Department of Neurology          neurological examination. The problem however is that
                                          Brain Research Institute        most diagnostic SPECT studies have not been done in this
                                                Niigata University        clinical setting: most involve later-stage clearly-defined pa-
                                                   Niigata, Japan         tients that are obviously not representative for this clinical
                                 *E-mail:       question. In our literature analysis, we found only 32 clin-
                                                                          ically relevant papers on a total of 185.3
                                                                                                         Wim E.J. Weber, MD, PhD*
 1. Kanazawa M, Shimohata T, Sato M, Onodera O, Tanaka K,                                                Annemarie M.M. Vlaar, MD
    Nishizawa M. Botulinum toxin A injections improve apraxia of
                                                                                                             Department of Neurology
    eyelid opening without overt blepharospasm associated with neu-
    rodegenerative diseases. Mov Disord 2007;22:597-598.                                               University Hospital Maastricht
 2. Lepore FE, Duvoisin RC. “Apraxia” of eyelid opening: an invol-                                                         Maastricht
    untary levator inhibition. Neurology 1985;35:423-427.                                                                  Netherland
 3. Jankovic J. Pretarsal injection of botulinum toxin for blepharo-                                *E-mail:
    spasm and apraxia of eyelid opening. J Neurol Neurosurg Psychi-
    atry 1996;60:704.                                                                            References
                                                                        1. Scherfler C, Schwarz J, Antonini A, et al. Role of DAT-SPECT in
                                                                           the diagnostic work up of Parkinsonism. Mov Disord 2007;22:
                                                                           1229 –1238.
                                                                        2. Vlaar AMM, de Nijs T, Kessels AGF, et al. Diagnostic value of
Role of DAT-SPECT in Diagnostic Work-Up of                                 FP-CIT and IBZM SPECT scans in 248 patients with parkinsonian
               Parkinsonism                                                syndromes. Eur Neurol 2008;59:258-266.
                                                                        3. Vlaar AM, van Kroonenburgh MJ, Kessels AG, Weber WE. Meta-
Scherfler et al1 present an extensive overview on the role of               analysis of the literature on diagnostic accuracy of SPECT in
                                                                           parkinsonian syndromes. BMC Neurol 2007;7:27.
DAT-SPECT scan in the diagnostic work-up of patients with
parkinsonism. We are impressed with the amount of work done
and we feel that their conclusions and recommendations are in
general justified. We would like to make a few remarks:
1. The authors state that “it is improbable that DAT imaging            Reply: Role of DAT SPECT in the Diagnostic
   would be normal in initial early disease” and that “patients                  Work-Up of Parkinsonism
   with normal striatal DAT availability are highly likely to
   suffer from diseases not affecting the nigrostriatal path-          Reply from the authors: We thank Dr. Weber for his comments.
   ways.” This suggests that a normal DAT scan could exclude           We would certainly be interested in his findings of patients with
   idiopathic Parkinson’s disease (IPD) in a patient with par-         a clinical diagnosis of parkinsonism exhibiting a normal DAT
   kinsonian signs and symptoms.                                       SPECT at baseline who later on developed abnormal scans.1
      We have recently finished a retrospective study on 248            Unfortunately the article he cites is still in press and currently
   patients who underwent SPECT imaging in a diagnostic                not accessible. As of now no published report exists describing
   work-up for parkinsonism.2 Of the 112 patients ultimately           patients— commonly turned SWEDDS— over the time of fol-
   diagnosed with IPD, 22 had an initial normal DAT scan. A            low up developing abnormal DAT binding on SPECT. There-
   number of these were rescanned after a certain period and           fore our statement about a normal DAT SPECT making a
   then an additional eight patients did have abnormal DAT             diagnosis of degenerative Parkinsonism unlikely is an accurate
   scans. This observation accords with a recent meta-analysis         reflection of the state of knowledge at the time of publication of
   we did, in which we found that a normal DAT scan in                 our article. If the pending publication by Dr. Weber and col-
   patients with a clinically undefined parkinsonism, does not          leagues will provide strong data to challenge this view remains
   rule out IPD.3                                                      to be seen.
                                                                          We agree with Dr. Weber that IBZM SPECT can be within
                                                                       normal limits in PSP, thereby adding little diagnostic informa-
  Published online 8 February 2008 in Wiley InterScience (www.         tion and we have stated this in the very sentence of our article DOI: 10.1002/mds.21952                        to which Dr. Weber is referring in his comment.2

Movement Disorders, Vol. 23, No. 5, 2008

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