Tremor associated with chronic inflammatory demyelinating peripheral neuropathy: treatment with pregabalin

Tremor

PURPOSE OF REVIEW

Tremor may be defined as an involuntary movement that is rhythmic (ie, regularly recurrent) and oscillatory (ie, rotating around a central plane) and may manifest in a variety of ways; accordingly, tremor has a rich clinical phenomenology. Consequently, the diagnosis of tremor disorders can be challenging, and misdiagnoses are common. The goal of this article is to provide the reader with straightforward approaches to the diagnosis and treatment of tremors.

RECENT FINDINGS

Focused ultrasound thalamotomy of the ventral intermediate nucleus of the thalamus is an emerging and promising therapy for the treatment of essential tremor.

SUMMARY

The evaluation should start with a detailed tremor history followed by a focused neurologic examination, which should attend to the many subtleties of tremor phenomenology. Among other things, the history and examination are used to establish whether the primary tremor is an action tremor (ie, postural, kinetic, or intention tremor) or a resting tremor. The clinician should then formulate two sets of diagnoses: disorders in which action tremor is the predominant tremor versus those in which resting tremor is the predominant tremor. Among the most common of the former type are essential tremor, enhanced physiologic tremor, drug-induced tremor, dystonic tremor, primary writing tremor, orthostatic tremor, and cerebellar tremor. Parkinson disease is the most common disorder of resting tremor. This article details the clinical features of each of these disorders, as well as those of additional tremor disorders.

Diagnosis and Management of Tremor

PURPOSE OF REVIEW

Tremor, which is a rhythmic oscillation of a body part, is among the most common involuntary movements. Rhythmic oscillations may manifest in a variety of ways; as a result, a rich clinical phenomenology surrounds tremor. For this reason, diagnosing tremor disorders can be particularly challenging. The aim of this article is to provide the reader with a straightforward approach to the diagnosis and management of patients with tremor.

RECENT FINDINGS

Scientific understanding of the pathophysiologic basis of tremor disorders has grown considerably in recent years with the use of a broad range of neuroimaging approaches and rigorous, controlled postmortem studies. The basal ganglia and cerebellum are structures that seem to play a prominent role.

SUMMARY

The diagnosis of tremor disorders is challenging. The approach to tremor involves a history and a neurologic examination that is focused on the nuances of tremor phenomenology, of which there are many. The evaluation should begin with a tremor history and a focused neurologic examination. The examination should attend to the many subtleties of tremor phenomenology. Among other things, the history and examination are used to establish whether the main type of tremor is an action tremor (ie, postural, kinetic, or intention tremor) or a resting tremor. The clinician should then formulate two sets of differential diagnoses: disorders in which action tremor is the predominant tremor versus those in which resting tremor is the main tremor. Among the most common of the former type are essential tremor, enhanced physiologic tremor, drug-induced tremor, dystonic tremor, orthostatic tremor, and cerebellar tremor. Parkinson disease is the most common form of resting tremor, along with drug-induced resting tremor. This article details the clinical features of each of these as well as other tremor disorders.

The treatment of tremor

Tremor is a hyperkinetic movement disorder characterized by rhythmic oscillations of one or more body parts. It can be disabling and may impair quality of life. Various etiological subtypes of tremor are recognized, with essential tremor (ET) and Parkinsonian tremor being the most common. Here we review the current literature on tremor treatment regarding ET and head and voice tremor, as well as dystonic tremor, orthostatic tremor, tremor due to multiple sclerosis (MS) or lesions in the brainstem or thalamus, neuropathic tremor, and functional (psychogenic) tremor, and summarize main findings. Most studies are available for ET and only few studies specifically focused on other tremor forms. Controlled trials outside ET are rare and hence most of the recommendations are based on a low level of evidence. For ET, propranolol and primidone are considered drugs of first choice with a mean effect size of approximately 50 % tremor reduction. The efficacy of topiramate is also supported by a large double-blind placebo-controlled trial, while other drugs have less supporting evidence. With a mean effect size of about 90 % deep brain stimulation in the nucleus ventralis intermedius or the subthalamic nucleus may be the most potent treatment; however, there are no controlled trials and it is reserved for severely affected patients. Dystonic limb tremor may respond to anticholinergics. Botulinum toxin improves head and voice tremor. Gabapentin and clonazepam are often recommended for orthostatic tremor. MS tremor responds only poorly to drug treatment. For patients with severe MS tremor, thalamic deep brain stimulation has been recommended. Patients with functional tremor may benefit from antidepressants and are best be treated in a multidisciplinary setting. Several tremor syndromes can already be treated with success. But new drugs specifically designed for tremor treatment are needed. ET is most likely covering different entities and their delineation may also improve treatment. Modern study designs and long-term studies are needed.

Tremor in inflammatory neuropathies

BACKGROUND

Tremor is known to occur in patients with neuropathies although its reported prevalence varies widely. Tremor has been shown to cause disability in children with Charcot-Marie-Tooth disease but no data exit about the disability caused by tremor in inflammatory neuropathies. Little is known about the response of neuropathic tremor to treatment and why it selectively occurs in some people and not others.

METHODS

This case control study investigates the presence and severity of tremor in 43 consecutively recruited patients with inflammatory neuropathies at the National Hospital for Neurology and Neurosurgery, London. Clinical assessment, including Fahn-Tolosa-Marin Scale for tremor, sensory scores, power scores and Overall Neuropathy Limitations Scale, were recorded. Results of nerve conduction studies were retrieved and assessed. Nine patients' tremors were recorded with accelerometry.

RESULTS

Tremor was most common in IgM paraproteinaemic neuropathies, as previously reported, but also occurred in 58% of those with chronic inflammatory demyelinating polyradiculoneuropathy and 56% of those with multifocal motor neuropathy with conduction block. We describe, for the first time, tremor in the majority of patients with multifocal motor neuropathy with conduction block. Tremor in all of these patients seems generally refractory to treatment except in a small number of cases where tremor improves with treatment of the underlying neuropathy. We provide evidence that tremor may add to disability in patients with inflammatory neuropathy. Mean tremor frequency was 6 Hz and did not vary with weight loading. We demonstrate for the first time that although tremor severity correlates with F wave latency, it is not sufficient to distinguish those with, from those without, tremor.

CONCLUSION

Tremor in inflammatory neuropathies is common, adds to disability and yet does not often respond to treatment of the underlying neuropathy. When present, tremor severity is associated with F wave latency.

Chronic pain as a manifestation of potassium channel-complex autoimmunity

OBJECTIVE

Autoantibodies targeting voltage-gated potassium channel (VGKC) complexes cause a spectrum of neuronal hyperexcitability disorders. We investigated pain as a manifestation of VGKC-complex autoimmunity.

METHODS

We reviewed the prevalence and characteristics of pain in VGKC-complex-immunoglobulin G (IgG)-seropositive patients in 25 months of comprehensive service testing for neural autoantibodies, subtyped positive sera for LGI1-IgG and CASPR2-IgG specificities, and reviewed pain prevalence in autoimmune control patients.

RESULTS

VGKC-complex-IgG was identified in 1,992 patients of 54,853 tested (4%). Of 316 evaluated neurologically at Mayo Clinic, 159 (50%) had pain, in isolation (28%) or with accompanying neurologic manifestations (72%), and not attributable to alternative cause. Pain was subacute in onset, chronic in course, neuropathic, nociceptive, regional, or diffuse and sometimes attributed to fibromyalgia (6%) or psychogenic cause (13%). Most patients had normal peripheral nervous system function, measured by neuropathy impairment scores and nerve conduction. Evidence of neuronal hyperexcitability (hyperhidrosis, quantitative heat-pain hyperalgesia, or electromyographic excitability) was 25-fold more common in pain patients. Pain management required multiple medications in 70% (narcotics, 30%); 13 of 16 patients reported pain relief with immunotherapy. Pain was significantly associated with CASPR2-IgG-positivity (16% positive with pain, 7% without pain; p = 0.014) but not with LGI1-IgG. Less than 10% of 167 patients with neural autoantibodies other than VGKC-complex-IgG reported pain.

CONCLUSIONS

Chronic idiopathic pain is a syndromic manifestation of VGKC-complex autoimmunity. Hyperexcitability of nociceptive pathways is implicated. CASPR2-IgG significantly associates with pain, but in most patients the antigenic VGKC-complex molecule remains to be determined. VGKC-complex autoimmunity represents an important new direction for pain research and therapy.