Undulating Tongue Revealing Wilson's Disease

Clinical Neurology in Practice: The Tongue (part 2)

BACKGROUND

The tongue is an essential organ for the development of certain crucial functions such as swallowing and speech. The examination of the tongue can be very useful in neurology, as the various types of lingual alterations can lead to certain specific diagnoses, the tongue being a kind of 'mirror' of some neurological function.

REVIEW SUMMARY

To discuss the elements of clinical examination of the tongue in relation to neurological disorders. After reviewing the different superficial lesions of the tongue, we deal with various movement disorders of the tongue (fasciculations/myokimia, orolingual tremor, choreic movements of the tongue, dystonia of the tongue, lingual myoclonus, and psychogenic movements), disorders of taste and lingual sensitivity and lingual pain.

CONCLUSIONS

Examination of the tongue should not be limited to studying its motility and trophicity. It is equally important to check the sensory function and understand how to interpret abnormal movements involving the tongue. This study also aimed to demonstrate the importance of nonmotor tongue function in neurological practice.

A Case Series of Patients With MYBPC1 Gene Variants Featuring Undulating Tongue Movements as Myogenic Tremor

Myosin-binding protein C1 (MYBPC1) encodes myosin-binding protein C, slow type (sMyBP-C), an accessory protein that regulates actomyosin cross-linking, stabilizes thick filaments, and modulates contractility in muscle sarcomeres and has recently been linked to myopathy with tremor. The clinical features of MYBPC1 mutations manifesting in early childhood bear some similarities to those of spinal muscular atrophy (SMA), such as hypotonia, involuntary movement of the tongue and limbs, and delayed motor development. The development of novel therapies for SMA has necessitated the importance of differentiating SMA from other diseases in the early infancy period. We report the characteristic tongue movements of MYBPC1 mutations, along with other clinical findings, such as positive deep tendon reflexes and normal peripheral nerve conduction velocity testing, which could help in considering other diseases as differential diagnoses.

Isolated and combined genetic tremor syndromes: a critical appraisal based on the 2018 MDS criteria

The 2018 consensus statement on the classification of tremors proposes a two-axis categorization scheme based on clinical features and etiology. It also defines "isolated" and "combined" tremor syndromes depending on whether tremor is the sole clinical manifestation or is associated with other neurological or systemic signs. This syndromic approach provides a guide to investigate the underlying etiology of tremors, either genetic or acquired. Several genetic defects have been proven to cause tremor disorders, including autosomal dominant and recessive, X-linked, and mitochondrial diseases, as well as chromosomal abnormalities. Furthermore, some tremor syndromes are recognized in individuals with a positive family history, but their genetic confirmation is pending. Although most genetic tremor disorders show a combined clinical picture, there are some distinctive conditions in which tremor may precede the appearance of other neurological signs by years or remain the prominent manifestation throughout the disease course, previously leading to misdiagnosis as essential tremor (ET). Advances in the knowledge of genetically determined tremors may have been hampered by the inclusion of heterogeneous entities in previous studies on ET. The recent classification of tremors therefore aims to provide more consistent clinical data for deconstructing the genetic basis of tremor syndromes in the next-generation and long-read sequencing era. This review outlines the wide spectrum of tremor disorders with defined or presumed genetic etiology, both isolated and combined, unraveling diagnostic clues of these conditions and focusing mainly on ET-like phenotypes. Furthermore, we suggest a phenotype-to-genotype algorithm to support clinicians in identifying tremor syndromes and guiding genetic investigations.