Thalamotomy for Focal Hand Dystonia

History

Writer’s cramp was first reported by Charles Bell in 1833. Bell described “I have found the action necessary for writing gone, whilst the power of strongly moving the arm, or fencing, remained,” and he named the condition as “scrivener’s palsy. I consider that Bell used the term palsy to express “movement disorder” instead of “motor weakness.” In 1888, a British neurologist, Gowers, named the condition occupational neurosis. I think this was the beginning of the confusion between neurological and psychogenic origins of writer’s cramp because neurosis in German medicine around that time meant neurotic psychosis, and German medicine had a strong influence on other countries. However, Gowers used neurosis to mean a neurological disorder. Since then, there have been extensive discussions on the genesis of writer’s cramp. In 1861, French neurologist Duchenne described, “I must confess that I am unable to solve this important problem. However, rationally, I believe that this disorder is the result of a central nervous system disorder. This disorder is serious, as it resists all forms of treatment, even faradic treatment.” The concept of dystonia was not present until Oppenheim proposed the term dystonia musculorum deformans in 1911, which is today’s DYT1 generalized dystonia. In the 1960s and 1970s, Cooper found that some patients with dystonia musculorum deformans had a history of writer’s cramp as an initial symptom, and he suggested that writer’s cramp may be a type of dystonia. ^,

In 1982, Sheehy and Marsden reported their results of a comparison between patients with and without writer’s cramp. There was no difference of psychogenic factors between the groups, and they concluded that writer’s cramp is a physical illness rather than a psychological disturbance, and that it is a focal dystonia. Thus the concept of writer’s cramp as a focal hand dystonia was finally established in the early 1980s, when most functional stereotactic operations were declining and several articles reported disappointing results in the treatment of dystonia with thalamotomy. Surgery for dystonia in those days was not for FHD but for more widespread generalized dystonias. A large series of Cooper’s thalamotomy and pallidotomy for dystonia in the 1960s was before the concept of FHD was established. Since then, there have been many reports supporting that writer’s cramp and musician’s cramp are not psychogenic but neurological disorders.

There have been few reports on neurosurgical treatment of FHD until the 2000s. Siegfried et al. reported a case of cure of tremulous writer’s cramp by stereotactic thalamotomy in 1969. This case was probably tremor-dominant focal hand dystonia that is occasionally seen in FHD patients. Mempel et al. reported successful results of cryothalamotomy for writer’s cramp syndrome in 1986 in Polish language. Dr. Sobstyl in Poland, a pupil of Mempel, recently translated it to English (unpublished). They treated three patients with not only FHD but with some other forms of dystonia in other parts of the body including the face. The target covered a large area of the ventrolateral nucleus of the thalamus, and the final lesion size was 6 × 6 × 8 mm. They reported that writer’s cramp symptoms completely disappeared in all patients. Because this article was not written in English and the method (cryosurgery) was out of date, most neurosurgeons did not realize the importance of this report. Goto et al. reported excellent results of stereotactic selective Vo-complex thalamotomy in a patient with dystonic writer’s cramp in 1997.

I myself had studied the effect of thalamotomy on dystonias in the late 1980s without realizing the negative impact of writer’s or occupational cramp on the patients’ professional life. This was reported in 1989 at the 10th meeting of the World Society for Stereotactic and Functional Neurosurgery. It says, “Immediate improvement occurred in patients with focal limb dystonia,” “Improvement was sustained in patients with focal limb dystonia,” and “Focal limb dystonia can be greatly improved by thalamotomy without any motor, sensory or intellectual disturbance.” These findings are completely consistent with our recent experience of Vo thalamotomy described in this chapter.

In the 1990s, we saw a resurgence of interest in the neurosurgical management of dystonias. This was mainly because of the introduction of selective peripheral denervation for cervical dystonia (CD), Laitinen’s postero-ventro-lateral pallidotomy, and deep brain stimulation (DBS). Dystonia musculorum deformans was renamed young-onset DYT1 hereditary dystonia, and it was found to be the best indication of globus pallidus internus (GPi) pallidotomy. Pallidotomy was replaced with pallidal DBS, not only in the management of Parkinson disease but also in dystonias. However, it should be remembered that there has been no scientific comparison between GPi DBS and pallidotomy for dystonias, and DBS is neither effective nor safer than bilateral pallidotomy for idiopathic and inherited dystonia. In pallidal surgeries for generalized dystonia, the effect may often be delayed for months, and this is not consistent with the findings of thalamotomy for focal hand dystonia in which the surgical effect is immediate. During the 1990s, thalamotomy for dystonia was almost forgotten because the effect of pallidal operations on generalized dystonias revealed to be dramatic; thalamotomy for generalized dystonia had shown only modest improvement and great risks, especially in bilateral operations; and TSFHD was not considered in general to be the subject of surgical treatment.

I had been performing pallidal operations for generalized dystonias and peripheral denervation surgery for CD, and one day in 2000, a patient with writer’s cramp came to see me asking for surgical treatment. She said that her writer’s cramp is a type of dystonia and it should improve with brain surgery. She was a professional cartoon artist and had become unable to continue her professional activities as a result of writer’s cramp. I did not have any experience with surgical treatment for writer’s cramp. Her symptom seemed so mild to me as to hesitate surgical intervention. I searched for references, found a few case reports as mentioned earlier, and finally decided to try Vo-complex thalamotomy as described by Goto et al. This was the first case of my series of surgical treatment of FHD. The effect was surprisingly dramatic. The patient returned to the profession and finally, in 2008, she was recorded in Guinness World Records as the most selling cartoon artist in the world. I always recall the old description by Poore in 1887 about “piano failure.” He wrote, “When I use the word “minor,” please remember that they are minor only to our eyes, and in pathological sense. They are of maximum importance to the sufferer, who possibly sees his livelihood in jeopardy.”

Diagnosis of Focal Hand Dystonia

The diagnosis of FHD is basically made by history taking and inspection. There are no useful laboratory or imaging studies, although there are many reports on functional changes of the cerebral cortex detected with MRI. Most patients first see an orthopedician, considering that the symptom may be related to muscle or tendon problems caused by overuse. Generally, however, FHD is not accompanied by pain. The idiosyncrasies of movements are always associated with a specific task such as writing, drawing, playing musical instruments, or using special tools that require highly repetitive movements or extreme motor precision. Most patients have a history of extensive use of the fingers for very skilled and precise movements.

The three features that are important in the diagnosis of FHD are task specificity, stereotypy, and morning benefit. The symptom only appears when the patient does a specific task such as writing, using scissors, or playing an instrument. About 70% of such patients experience no symptoms at all when doing other tasks like using a knife, using chopsticks, or typing. The remaining 30% may have dystonic symptoms triggered by multiple tasks. The symptoms are always the same and constant. They may be milder in the morning in the early stage of the disease. In a few patients, the dystonic symptom becomes so severe that task specificity is lost, and the symptom persists all the time when they are awake. Very few patients develop dystonic symptoms in other parts of the body. Especially when the onset of FHD is in young age (younger than 20 years), ^, DYT1 dystonia should be suspected. In ordinary writer’s cramp, family history is exceptional.

Differential diagnoses include primary pure writing tremor, essential tremor, and peripheral injury–induced focal dystonia. ^, Primary writing tremor is task-specific tremor that appears only when writing. This is usually unilateral and does not respond to medications used for control of essential tremor or Parkinson disease. This condition may be a form of tremor-dominant writer’s cramp or dystonic tremor. Thalamotomy of the ventral intermediate nucleus (Vim) can effectively control pure writing tremor. Laypeople often use the term writer’s cramp when they cannot write as a result of tremor. Most of them, however, often do not have FHD but essential tremor. We must make a clear distinction between FHD and other types of involuntary movements of the hand. Some patients with FHD may have tremor, which is also task-specific but irregular and not rhythmic. We may call such tremor in dystonia patients dystonic tremor. If a patient has both dystonia and dystonic tremor of the hand, stereotactic ablation of both the Vo and Vim nuclei of the thalamus can control the symptoms ( Video 119.2, Video 119.3 ). FHD shows symptoms of various combinations of degrees of task specificity, dystonic symptoms, and tremor, as shown in Fig. 119.1 .