Editorial commentary

Diagnosis on shaky grounds Victor S C Fung The traditional neurological method consists of first deducing, from the symptoms and signs, ‘Where is the lesion?’, and then from additional history such as the temporal course, general medical and family history, deducing ‘What is the lesion?’. In a patient with a movement disorder, no matter what the symptoms and signs, localisation ends up back in the basal ganglia and one is no further along the diagnostic process. Therefore, a different diagnostic approach is needed. First, one assesses the phenomenology and then formulates a syndromic diagnosis, which in turn allows the generation of an aetiological differential diagnosis which forms the basis of further investigations and management.1 For example, the differential diagnosis of a patient presenting with myoclonus and dystonia varies from that of a patient presenting with chorea and dystonia. It is in the context of the neurological method described above that the article by Erro et al2 is of significance. Parkinson emphasised the importance of tremor at rest—‘in parts not in action and even when supported’ in his essay on the ‘Shaking Palsy’.3 It has been suggested that rest tremor is a dopaminergic symptom.4 However, unlike akinesia and rigidity, tremor severity does not correlate with the severity of nigrostriatal dopaminergic deficit,5 with cerebello-thalamocortical circuits playing a major role in determining rest tremor amplitude.6 Although rest tremor is mentioned as early as in Oppenheim’s seminal description of dystonia7 and Critchley’s descripits tion of essential tremor,8 pathophysiology and prevalence in these conditions has not been well studied, in part because of the lack of a clear biomarker for these diseases. In recent years, it has become established that a syndrome that mimics parkinsonism with rest tremor can be seen in the absence of a nigrostriatal deficit, at least as measured by dopaminergic imaging (so-called patients with scans without evidence of dopaminergic deficit, 11 or SWEDDs).9 10 Schneider et al have Correspondence to Dr Victor Fung, Movement Disorders Unit, Department of Neurology, Westmead Hospital, Westmead, Sydney, NSW 2145 Australia; [email protected]

gone on to suggest that some of these patients may have adult-onset dystonic tremor. However, this proposal has remained somewhat controversial, with a recent publication in this journal failing to identify rest tremor in 429 patients with primary adult-onset dystonia, of whom 16.7% were found to have tremor.12 In the present study, Erro et al2 prospectively examined for head and arm tremor in 473 consecutive patients with various forms of adult-onset primary dystonia. Tremor was present in 262 (55.4%). They found rest tremor of the upper limbs in 12% of their subjects, which was unilateral in 2/3, although associated postural tremor was always present. This observation gives an estimate of the prevalence of rest tremor of the upper limbs in primary adult-onset dystonia and establishes that it is not a rare phenomenon. Therefore, rest tremor should not be assumed to be due to Parkinson’s disease. To make things even more difficult, it has also been established that patients with SWEDDs may have an impairment of finger tapping similar to Parkinson’s disease,13 a similar latency to onset of re-emergent postural tremor,13 14 and decreased armswing.11 The study by Erro et al2 also raises some important questions. What should be classified as true rest tremor? The authors examined their patients with ‘arms relaxed in the lap’, but do not specify in what position. Was the upper limb resting fully supported with the hands pronated, or resting on their sides as is commonly done in clinical practice, but which may not result in as complete muscle relaxation? For example, in essential tremor, apparent ‘rest’ tremor, when the arms are supported but hands hanging in mid-air, can be eliminated if the hands are fully supported.15 Was rest tremor also present when patients were standing or walking, conditions not systematically observed in the present study. What was the effect of provocation manoeuvres which have been shown to enhance the amplitude of rest tremor in Parkinson’s disease16? In summary, rest tremor has been firmly established as part of the phenomenology of primary adult-onset dystonia. That tremulous movement can occur in dystonia has also been explicitly acknowledged in the

Fung VSC. J Neurol Neurosurg Psychiatry September 2014 Vol 85 No 9

new consensus definition of dystonia.17 The syndromic diagnosis of unilateral upper limb rest tremor, impaired finger tapping and reduced armswing should no longer be equated with parkinsonism or Parkinson’s disease. Rest in pieces. Competing interests None. Patient consent Obtained. Provenance and peer review Commissioned; internally peer reviewed.

To cite Fung VSC. J Neurol Neurosurg Psychiatry 2014;85:947–948. Received 21 October 2013 Accepted 24 October 2013 Published Online First 22 November 2013

▸ http://dx.doi.org/10.1136/jnnp-2013-305876 J Neurol Neurosurg Psychiatry 2014;85:947–948. doi:10.1136/jnnp-2013-306538

REFERENCES 1

2

3 4

5

6

7 8 9

10

11

12

Fung VSC, Morris JGL. Parkinson’s disease and other movement disorders. In: Warlow C, ed. The Lancet handbook of treatment in neurology: Elsevier, 2006:127–60. Erro R, Rubio-Agusti I, Saifee TA, et al. Rest and other types of tremor in adult-onset primary dystonia. J Neurol Neurosurg Psychiatry 2014;85:965–8. Parkinson J. An essay on the shaking palsy. 1st edn. London: Wittington and Newland, 1817. Deuschl G, Papengut F, Hellriegel H. The phenomenology of parkinsonian tremor. Parkinsonism Relat Disord 2012;18(Suppl 1):S87–9. Vingerhoets FJ, Schulzer M, Calne DB, et al. Which clinical sign of Parkinson’s disease best reflects the nigrostriatal lesion? AnnNeurol 1997;41:58–64. Helmich RC, Hallett M, Deuschl G, et al. Cerebral causes and consequences of parkinsonian resting tremor: a tale of two circuits? Brain 2012;135(Pt 11):3206–26. Klein C, Fahn S. Translation of Oppenheim’s 1911 paper on dystonia. Mov Disord 2013;28:851–62. Critchley M. Observations on essential (heredofamilial) tremor. Brain 1949;72:113–39. Marek K, Seibyl J, Group PS. b-CIT scans without evidence of dopaminergic deficit (SWEDD) in the ELLDOPA-CIT and CALM-CIT study: longterm imaging assessment. Neurology 2003;60(Suppl 1):A298. Marshall VL, Patterson J, Hadley DM, et al. Successful antiparkinsonian medication withdrawal in patients with Parkinsonism and normal FP-CIT SPECT. Mov Disord 2006;21:2247–50. Schneider SA, Edwards MJ, Mir P, et al. Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs). Mov Disord 2007;22:2210–15. Defazio G, Gigante AF, Abbruzzese G, et al. Tremor in primary adult-onset dystonia: prevalence and associated clinical features. J Neurol Neurosurg Psychiatry 2013;84:404–8.

947

Editorial commentary 13

14

948

Bajaj NP, Gontu V, Birchall J, et al. Accuracy of clinical diagnosis in tremulous parkinsonian patients: a blinded video study. J Neurol Neurosurg Psychiatry 2010;81:1223–8. Jankovic J, Schwartz KS, Ondo W. Re-emergent tremor of Parkinson’s disease. J Neurol Neurosurg Psychiatry 1999;67:646–50.

15

16

Burne JA, Hayes MW, Fung VS, et al. The contribution of tremor studies to diagnosis of parkinsonian and essential tremor: a statistical evaluation. J Clin Neurosci 2002;9:237–42. Raethjen J, Austermann K, Witt K, et al. Provocation of Parkinsonian tremor. Mov Disord 2008;23: 1019–23.

17

Albanese A, Bhatia K, Bressman SB, et al. Phenomenology and classification of dystonia: a consensus update. Mov Disord 2013;28: 863–73.

Fung VSC. J Neurol Neurosurg Psychiatry September 2014 Vol 85 No 9

Copyright of Journal of Neurology, Neurosurgery & Psychiatry is the property of BMJ Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Diagnosis on shaky grounds.

Diagnosis on shaky grounds. - PDF Download Free
367KB Sizes 0 Downloads 0 Views