Objective: The case of a patient with seropositive Myasthenia gravis (MG), presenting with forehead tremor, is reported.

Background: The clinical presentation of MG with involuntary movements was observed in an exiguous number of cases, but the association between MG and forehead tremor has not previously described. 

Methods: A 59-year-old man complained of rhythmic eyebrow movements with a fluctuating daily trend for 7 months. Neurological examination showed bilateral ptosis and forehead tremor, observable at rest and increasing in up-gaze. Single-Fiber-EMG of Orbicularis Oculi (OO) muscle documented a jitter value of 92 µs and 100% of pairs with pathological jitter. Brain-MR and chest-CT were negative. Titer of anti-acetylcholine-receptor antibodies was of 22 nmol/L. Patient also underwent facial tremor recording by surface electrodes on Frontalis (F) and OO muscles. An irregular bilateral activity of F muscles with frequency of 4-6 Hz, increasing in amplitude during up-gaze, was recorded. Antagonistic OO muscles activity was absent. Pyridostigmine 360 mg and prednisone 50 mg daily were administered with clinical improvement of ptosis and forehead tremor.

Results: The association between movement disorders and MG was firstly pointed out in 1967 with the description of palpebral tremor in a MG patient (1). The co-occurrence of MG and opsoclonus-myoclonus syndrome (2) was also reported. Forehead tremor has been very rarely described in patients with Parkinson’s disease, Essential Tremor and focal dystonia. In this report, we described a patient with forehead tremor as presentation sign of MG. EMG tremor pattern is usually featured by the presence of alternating or synchronous contraction of agonist-antagonist muscles. Antagonist muscles activity was absent in this case. The pathophysiologic process below this clinical feature is unknown. We hypothesized that typical F and OO weakness of ocular MG could explain the onset of forehead tremor as a compensatory act for keeping eyes open, clinically resembling tremor, despite neurophysiological recording was not typical of tremor. 

Conclusions: To our knowledge, this is the first description of forehead tremor as clinical presentation of MG. Forehead tremor was only observed in extrapyramidal syndromes. When a patient presents with forehead tremor, with or without ocular symptoms, we should consider also MG in differential diagnosis, in order to start rapidly the adequate treatment.

References: 1)    Ito S, Ito H. Palpebral minor tremor in myasthenia gravis. Nippon Ganka Gakkai Zasshi. 1967; 71(1):15-21. 
2)    Wilfong AA, Fernandez F. Myasthenia gravis in a child with sequelae of opsoclonus-myoclonus syndrome. Can J Neurol Sci 1992; 19(1):88-89.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/forehead-tremor-a-clinical-presentation-of-ocular-myasthenia-gravis/