Voluntary palatal tremor is associated with hyperactivation of the inferior olive: a functional magnetic resonance imaging study

Palatal Tremor - Pathophysiology, Clinical Features, Investigations, Management and Future Challenges

Background:

Palatal tremor is involuntary, rhythmic and oscillatory movement of the soft palate. Palatal tremor can be classified into three subtypes; essential, symptomatic and palatal tremor associated with progressive ataxia.

Methods:

A thorough Pubmed search was conducted to look for the original articles, reviews, letters to editor, case reports, and teaching neuroimages, with the keywords “essential”, “symptomatic palatal tremor”, “myoclonus”, “ataxia”, “hypertrophic”, “olivary” and “degeneration”.

Results:

Essential palatal tremor is due to contraction of the tensor veli palatini muscle, supplied by the 5^th cranial nerve. Symptomatic palatal tremor occurs due to the contraction of the levator veli palatini muscle, supplied by the 9%^th and 10%^th cranial nerves. Essential palatal tremor is idiopathic, while symptomatic palatal tremor occurs due to infarction, bleed or tumor within the Guillain-Mollaret triangle. Progressive ataxia and palatal tremor can be familial or idiopathic. Symptomatic palatal tremor and sporadic progressive ataxia with palatal tremor show signal changes in inferior olive of medulla in magnetic resonance imaging. The treatment options available for essential palatal tremor are clonazepam, lamotrigine, sodium valproate, flunarizine and botulinum toxin. The treatment of symptomatic palatal tremor involves the treatment of the underlying cause.

Discussion:

Further studies are required to understand the cause and pathophysiology of Essential palatal tremor and progressive ataxia and palatal tremor. Similarly, the link between tauopathy and palatal tremor associated progressive ataxia needs to be explored further. Oscillopsia and progressive ataxia are more debilitating than palatal tremor and needs new treatment approaches.

Clinical presentation and management of proatlas segmentation defect presenting with palatal myoclonus: case report

Clinical presentation of craniovertebral junction disorders may range from acute catastrophic neurological deficits to insidious signs and symptoms that may mask the underlying etiology. Prompt recognition and treatment is essential to avert long-term neurological morbidity. Proatlas segmentation disorders are a rare group of developmental disorders involving the craniocervical junction. Abnormal bony segmentation leads to malformed bony structures that can in turn lead to neurological deficits through bony compression of the cervicomedullary junction. This report details a proatlas segmentation defect presenting as palatal myoclonus, a rare movement disorder. The clinical presentation, surgical management, and neuroanatomical basis for the disorder is presented. This report highlights the myriad clinical presentations of craniovertebral disorders and emphasizes a rare but treatable etiology for palatal myoclonus.

Recognizing uncommon presentations of psychogenic (functional) movement disorders

BACKGROUND

Psychogenic or functional movement disorders (PMDs) pose a challenge in clinical diagnosis. There are several clues, including sudden onset, incongruous symptoms, distractibility, suggestibility, entrainment of symptoms, and lack of response to otherwise effective pharmacological therapies, that help identify the most common psychogenic movements such as tremor, dystonia, and myoclonus.

METHODS

In this manuscript, we review the frequency, distinct clinical features, functional imaging, and neurophysiological tests that can help in the diagnosis of uncommon presentations of PMDs, such as psychogenic parkinsonism, tics, and chorea; facial, palatal, and ocular movements are also reviewed. In addition, we discuss PMDs at the extremes of age and mass psychogenic illness.

RESULTS

Psychogenic parkinsonism (PP) is observed in less than 10% of the case series about PMDs, with a female-male ratio of roughly 1:1. Lack of amplitude decrement in repetitive movements and of cogwheel rigidity help to differentiate PP from true parkinsonism. Dopamine transporter imaging with photon emission tomography can also help in the diagnostic process. Psychogenic movements resembling tics are reported in about 5% of PMD patients. Lack of transient suppressibility of abnormal movements helps to differentiate them from organic tics. Psychogenic facial movements can present with hemifacial spasm, blepharospasm, and other movements. Some patients with essential palatal tremor have been shown to be psychogenic. Convergence ocular spasm has demonstrated a high specificity for psychogenic movements. PMDs can also present in the context of mass psychogenic illness or at the extremes of age.

DISCUSSION

Clinical features and ancillary studies are helpful in the diagnosis of patients with uncommon presentations of psychogenic movement disorders.

Oculopalatal tremor: current concepts and new observations

PURPOSE OF REVIEW

Oculopalatal tremor (OPT) is an acquired disorder resulting from the interruption of a specific brainstem circuitry, the dentato-rubro-olivary pathway or Guillain-Mollaret triangle. The recent literature on OPT and olivary hypertrophy was reviewed with specific interest regarding causes, diagnostic procedures, physiopathology and therapies.

RECENT FINDINGS

OPT is associated with inferior olivary hypertrophy, and recent findings have provided a better understanding of its intimate mechanisms. A dual-mechanism model, combining an oscillator (inferior olive) and a modulator/amplifier (cerebellum), best explains the development of OPT. Electrotonic coupling and specific Ca channels contribute to oscillations of inferior olivary nucleus neurons in OPT. Improvement of visual symptoms can be achieved with oral gabapentin or memantine.

SUMMARY

Both the neuronal circuitry and the physiopathology of OPT are now better understood. This opens up an era of specific therapy for this rare cause of disabling oscillopsia.

In vivo structural and functional imaging of the human rubral and inferior olivary nuclei: A mini-review

Few imaging studies have been devoted to the structural and functional connectivity of the red and inferior olivary nuclei although these two nuclei represent two main targets of the cerebellum within the brainstem. However, the RN is anatomically and functionally related to a widespread sensorimotor, limbic, and executive brain network. It projects massively onto the principal olive with which it contributes to a cerebello-rubro-olivo-cerebellar loop modulated by cortical and subcortical afferents. Despite a minor role in planning and execution of rhythmic movements, the red nucleus in conjunction with the inferior olive, more specifically involved in the detection of "unexpected" events, contributes to sensorimotor, sensory and, likely, cognitive higher functions.

New device to control combined lingual and palatal myoclonus

Lingual myoclonus is a poorly understood disorder that may occur in isolation or combined with palatal myoclonus. In this report, we present the case history of a 21-year-old patient with a therapy-resistant essential lingual and palatal myoclonus where a simple dental device was able to control symptoms. The use of this device will be highlighted and compared to previously described methods. Cases of previously recorded lingual and palatal myoclonus will be reviewed and compared to the case of our patient.

Endonasal approach of salpingopharyngeus muscle for the treatment of ear click related to palatal tremor

Palatal tremor (PT) is a rare disease associated with rhythmic movements of the soft palate. It can be separated into two distinct clinical entities: symptomatic and essential. Most patients with essential PT complain of the rhythmic ear clicks and in some cases tinnitus, but usually have an uneventful medical history. Symptomatic PT patients are often unaware of the palatal movements and have symptoms and signs of brainstem or cerebellar dysfunction. We describe the case of a 25-year-old patient who developed severe essential PT, with very distressing bilateral objective tinnitus, constantly perceived as ear clicks. Several oral medications were prescribed with poor results. No significant improvement was obtained with repetitive injections of botulinum toxin type A (BTX A) distributed in soft palate muscles. Because of the continuous tinnitus and its impact on the patient's quality of life, chemical denervation of the salpingopharyngeus muscles, which is involved in the production of tinnitus, with BTX A was performed endonasally under endoscopic guidance. The result was very satisfactory. Tinnitus due to essential PT may be satisfactorily treated by endonasal injection of BTX into the salpingopharyngeus and palatopharyngeus muscles.

The 'essentials' of essential palatal tremor: a reappraisal of the nosology

Essential palatal tremor (EPT) is an uncommon disorder, distinct from symptomatic palatal tremor (SPT), but characterized by superficially similar rhythmic movements of the soft palate. While the pathophysiology of SPT has been relatively well defined, this is not the case in EPT. Based on an analysis of 103 published cases, we reviewed EPT in the context of other movement disorders with similar features and outline possible pathophysiological mechanisms. Phenomenologically it remains best classified as a tremor. Four major causes, including a central generator, peripheral/mechanical, voluntary/special skill and psychogenic, appear to account for the majority of cases of EPT, although there is considerable overlap in the pathogenic mechanisms underlying these categories. Among the cases reviewed, a large proportion fit into the latter two categories, although there are others where multiple mechanisms are likely at play. Based on our reappraisal, we suggest a change in designation to 'isolated palatal tremor', with primary and secondary subtypes. This retains the distinction from SPT and emphasizes the non-uniform, heterogeneous nature of the disorder.

Voluntary control and a wider clinical spectrum of essential palatal tremor

Essential palatal tremor (EPT) may not be a uniform or single entity. We present two patients who had some "voluntary control" over EPT, including entrainment. We review the English language literature on EPT to describe a wider clinical spectrum of this syndrome.

Modulation of cerebellar activation by predictive and non-predictive sequential finger movements

We investigated the modulation of cerebellar activation by predictive and non-predictive sequential finger movements. It is hypothesized that the prediction of desired movement sequences and adaptation to new movement parameters is mediated by the cerebellum. Using functional MRI at 1.5 T, seven normal subjects performed sequential finger to thumb opposition movements, either in predictive (repeatedly 2,3,4,5) or non-predictive (randomized) fashion at a constant frequency of 1 Hz. Performance and error rates were monitored by simultaneous recording of the finger movements. Predictive sequential finger opposition movements activated a cerebellar network including the lobuli IV-VI ipsilateral to the movements, the contralateral lobuli IV-VI, the vermis, and lobuli VIIB-VIII ipsilaterally. Non-predictive compared to predictive finger opposition movements activated a broader area within the ipsi- and contralateral anterior cerebellum, lobuli IV-VI, the vermis, and the ipsilateral lobuli VIIB-VIII. Additional activation foci were found in the contralateral lobuli VIIA and VIIB-VIII. Our study demonstrates a modulated information processing within the cerebellar network dependent on the predictability of movement sequences.