PLME is defined as the association of aching or burning pain in at least one limb and involuntary movement of at least one finger or toe. The involuntary movement is spontaneous and continuous and characterized by flexion-extension and/or abduction-adduction movement of affected fingers or toes. Typically, the movement increases in proportion to the degree of pain and cannot be reproduced on the unaffected side. Some of the patients can stop the movement for a short time by conscious effort and the movement disappears during sleep. There are some reports of patients with PLME without pain, called painless limbs/moving extremities [2
We identified 12 patients with PLME of the upper extremity (PAMF), and of these patients, only one was successfully treated surgically [34
] (Table ). There are more reported cases of PLME in the lower extremity (PLMT) than in the upper extremities (PAMF). However, there have been no reports of PLMT being successfully resolved surgically, and only two reports of PLMT being partially or temporary improved surgically [14
] (Table ).
Review of the literature (painful arms and moving fingers)
Review of the literature (painful legs and moving toes)
PLME is a relatively rare disorder; therefore, the pathophysiology is not fully understood. Based on the effectiveness of the lumbar sympathetic ganglion block, Spillane et al. [32
] speculated that abnormal impulses from afferent fibers in the sympathetic nervous system activated ventral horn cells in the spinal cord, resulting in the involuntary movement. Nathan [17
] proposed that abnormal stimulation to the nerve root or peripheral nerve caused pain in the limbs and evoked involuntary movement by stimulating ventral horn cells via the spinal interneuron. Meanwhile, as involuntary movement does not appear during sleep, Schott suggested it was associated with the reticular activating system [28
], which is controlled by consciousness.
In our patients, the pain and involuntary movement disappeared after decompression or block of the spinal nerve root, supporting Nathan’s theory regarding the pathomechanism of PLME (Fig. ). He theorized that ectopic impulses of the nerve root caused by irritation are conducted to the spinal dorsal horn neurons through the afferent pathway, leading to pain perception. At the same time, the impulses from the nerve root would excite the local spinal interneuron and lead to stimulation of spinal ventral horn neurons, resulting in involuntary movement of the extremity.
Fig. 2 According to the interneuron theory of Nathan , pain is perceived through the lateral spinothalamic tract. The impulse excites the spinal interneuron and leads to stimulation of spinal ventral horn cells, resulting in involuntary movement of the extremity. (more ...)
Nonsurgical treatments, including administration of benzodiazepine or γ-aminobutyric acid and sympathetic ganglion block, are commonly performed [6
] for patients with PLME because the central nervous system or sympathetic nervous system also is considered to be the cause of PLME, as mentioned above. However, symptoms of PAMF (Table ) and PLMT (Table ) usually are resistant to such treatments.
Dressler et al. [4
] reported that sympathetic ganglion block was effective in approximately 50% of patients with PLME but the effects were transient. Guieu et al. [9
] treated two patients with PLMT by injection of adenosine triphosphate. The pain disappeared but the effect on movement was not mentioned. Okuda et al. [19
] suggested several advantages of epidural block over sympathetic ganglion block, and Takahashi et al. [36
] reported the benefit of epidural spinal cord stimulation for PLMT. Recently, treatment with botulinum toxin A (BTA) injection was reported by Singer and Papapetropoulos [31
] and Eisa et al. [7
]. The injection resulted in substantial pain relief and reduction of involuntary movement owing to reduction of the muscle spindle leading to decreased activity of the gamma loop and central sensitization.
Sudo et al. [34
] reported the only case of a patient with PAMF in whom pain and involuntary movement were resolved by surgery. In their patient, cervical radiculopathy or segmental myelopathy was thought to be the cause of the symptoms, and bilateral open-door laminoplasty was performed. Similarly, the symptoms in our first patient were resolved by decompression of the nerve root. Therefore, we believe surgical treatment should be considered for patients in whom compression of nerve tissue is recognized by MRI and/or CT but in whom no response is obtained by nonsurgical treatment.