Tremor

INDEX

This term is synonymous with:

  1. Benign tremulous PD
  2. Tremor-predominant parkinsonism or PD
  3. Monosymptomatic tremor at rest.

The last may be the best term, since on the one hand, it avoids making a potentially premature diagnosis of PD, which may later prove to be erroneous, and on the other, it emphasises diagnostic uncertainty.

Imaging of the nigrostriatal pathway is often of considerable value in patients with this clinical syndrome.

Neuropathology has suggested a lesser degree of nigral cell loss in this group of patients, as compared to controls with idiopathic PD1.

In general, knowledge of this condition is limited, and caution is called for, both with respect to determining the correct diagnosis, but also for prognosis.

ORIGIN

Tremor is unique in PD, since it is likely to have a pathophysiology different from other PD symptoms. In addition, tremor does not progress at the same rate as bradykinesia, rigidity, gait and balance disorders, and tremor severity does not correlate with other motor symptoms. Tremor responds less well to dopaminergic treatment than bradykinesia and rigidity (Koller et al., 1994; Fishman, 2008).

CLASSIFICATION

So-called “monosymptomatic resting tremor” was defined by the Consensus Statement of the Movement Disorder Society on Tremor2 with the following criteria :

CLINICAL FEATURES

Most of these patients develop into the tremor-dominant variant of PD, but this may last more than a decade. The clinical features of this tremor form are largely identical to classic Parkinsonian tremor, although it should be noted that action tremor is often reported, and thus that the tremor is not necessarily limited to a pure rest tremor.

The prognosis is not necessarily benign: Many patients develop the common features of advanced PD by the final third of their disease course.

DISTRIBUTION

Tremor virtually invariably involves the upper limb, predominantly the hand.

DIFFERENTIAL DIAGNOSIS

Note that misdiagnosis is common: the reason that patients may have apparent benign PD is that they do not actually have PD at all.

Dystonic Tremor: it is well accepted that dystonic tremor may mimic features of PD, such as rest tremor, and it would be anticipated that the course could be relatively benign.

Essential Tremor: rest tremor associated with ET is well known, but perhaps not sufficiently appreciated.  To reiterate, variants of ET exist, with a resting component to their tremor (but proven pathologically not to have Lewy pathology).

 

 

 

 

 

 

 

 

 

 

Differential diagnosis of Monosymptomatic Rest Tremor3

DIAGNOSTIC TESTS

If the dopaminergic system in patients with monosymptomatic rest tremor is assessed with F-DOPA PET scans or FP-CIT-dopamine transporter imaging, there is a similar dopaminergic depletion as is present in typical Parkinson’s disease. However, it is not known precisely when a nigrostriatal deficit in tremor predominant PD will develop and be demonstrated by imaging, although it appears reasonable to assume that the test is sensitive early on in the course of the illness.

TREATMENT:

Tremor is often poorly responsive to dopamine replacement therapy.

REFERENCES:

1. Selikhova M, Kempster PA, Revesz T, Holton JL, Lees AJ. Neuropathological findings in benign tremulous Parkinsonism. Mov Disord. 2013;28(2):145-152. doi:10.1002/mds.25220

2. Deuschl G, Bain P, Brin M, et al. Consensus statement of the Movement Disorder Society on Tremor. Ad Hoc Scientific Committee. Mov Disord. 1998;13 Suppl 3(S3):2-23. doi:10.1002/mds.870131303

3. Deuschl G. Benign tremulous Parkinson’s disease: A misnomer? Mov Disord. 2013;28(2):117-119. doi:10.1002/mds.25317