Painful Legs and Moving Toes: How to Diagnose and What to Do?

Abstract & Commentary

By Claire Henchcliffe, MD, Assistant Professor, Department of Neurology and Neuroscience, Weill Medical College, Cornell University. Dr. Henchcliffe serves on the speaker's bureau for GlaxoSmithKline, Teva, Boehringer Ingelheim, Schwarz Pharma, and Allergan.

Synopsis: Fourteen cases of the rare and difficult to treat "painful legs and moving toes" syndrome are presented. The cases included diverse etiologies—polyneuropathy, radiculopathy, or neuroleptic use—and half responded to GABAergic medications.

Source: Alvarez MV, et al. Case series of painful legs and moving toes: Clinical and electrophysiologic observations. Mov Disord 2008;23:2062-2066.

Painful legs and moving toes (PLMT) is a rare syndrome of pain in the legs and feet, usually preceding involuntary movements in the feet or toes. The authors of this report reviewed 4780 patients diagnosed with a movement disorder at the Mayo Clinic in Arizona from 1996-2006, and identified 14 cases of PLMT and its variants (age range, 25-84 years; mean, 69 years). Eight patients had "classic" PLMT, 2 had PLMT with painful hands and moving fingers (PHMF), 2 had painless legs and moving toes (P-LMT), and 2 had PLMT with painless hands and moving fingers (P-HMF).

Most patients sought evaluation specifically for pain, which was described mostly as burning, but also as numbness, shooting, aching, or dull. Limb movements included flexion-extension, fanning, clawing, and abduction-adduction, usually asymmetric, asynchronous, and partially suppressible. In one patient observed at night, the movements continued into light sleep (stages N1 and N2). Notably, 11 patients had clinical evidence of peripheral neuropathy, thought to be associated with lumbar stenosis (n = 3), Sjogren syndrome (n = 3), diabetes (n = 2), and 1 each with IgG polyclonal gammopathy, vitamin B12 deficiency, lupus erythematosus, and no known cause. Seven patients responded to either pregabalin (75-1500 mg daily) or gabapentin (300-2400 mg daily), but in the remainder no drug treatment was effective. Of the 3 cases without neuropathy, 1 had no discernable cause, but 2 were associated with neuroleptic use (ziprasidone, perphenazine), and each responded to stopping or switching the medication. Seven patients underwent surface electromyography to better characterize their movements. Random irregular bursts of activity or semicontinuous bursts were observed (80-1000 msec), sometimes with a semi-rhythmic pattern (0.5-1 Hz) and sometimes with co-contraction of antagonists and neighboring muscles (i.e., features of chorea and dystonia).

Commentary

PLMT is a rare movement disorder that is little known and poorly understood. Apart from one previous case series from the United Kingdom, descriptions have been limited to isolated case reports, so this study represents a significant addition to our body of knowledge. At face value, it should be a clear-cut diagnosis, but it is likely that in practice, some are misdiagnosed. If the involuntary movements are not observed, isolated pain or discomfort could easily be interpreted as peripheral neuropathy alone. Unexplained sensations coupled with a movement disorder could also be misdiagnosed as restless legs syndrome (RLS): It is therefore important to elicit any diurnal rhythm (RLS is almost always worse at night) and precipitants (RLS worsens with inactivity), and to observe the movements directly. The appearance and timing of periodic limb movements of sleep associated with the majority of RLS cases are unlike those of PLMT. A diagnosis of PLMT should then stimulate a search for its etiology. Since cases associated with peripheral neuropathy were overwhelmingly associated with underlying causes, including vitamin B12 deficiency, diabetes mellitus, and autoimmune disease in this series, a low threshold should be maintained for obtaining nerve conduction studies in anyone suspected of suffering from PLMT.

One interesting point raised in this study is that 2 cases were associated with neuroleptic use (as has been previously reported). The authors make a convincing point that neuroleptic-induced PLMT is distinct from tardive dyskinesia because of the associated pain (unusual in choreiform tardive syndromes) and location (unusual for tardive dyskinesias to be present in the toes). However, the relationship between these syndromes remains to be fully determined.

Finally, PLMT has traditionally been extremely challenging to treat. However, since half of the cases with neuropathy-associated PLMT responded either to pregabalin or gabapentin, these would appear to be the drugs of choice for first-line treatment.