Annals of Indian Academy of Neurology
LETTER TO THE EDITOR
Year
: 2020  |  Volume : 23  |  Issue : 3  |  Page : 417--418

Opercular syndrome presenting as trismus: An interesting finding


Maneesh Shakywar1, Kanchana Pillai1, Rajesh Kumar Singh1, Anuj Prabhakar2, Deepa Dash1, Rohit Bhatia1, Manjari Tripathi1,  
1 Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neuroradiology, All India Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Dr. Rajesh Kumar Singh
Department of Neurology, Room No 703, C.N. Centre, All India Institute of Medical Sciences, New Delhi - 110 029
India




How to cite this article:
Shakywar M, Pillai K, Singh RK, Prabhakar A, Dash D, Bhatia R, Tripathi M. Opercular syndrome presenting as trismus: An interesting finding.Ann Indian Acad Neurol 2020;23:417-418


How to cite this URL:
Shakywar M, Pillai K, Singh RK, Prabhakar A, Dash D, Bhatia R, Tripathi M. Opercular syndrome presenting as trismus: An interesting finding. Ann Indian Acad Neurol [serial online] 2020 [cited 2020 Aug 13 ];23:417-418
Available from: http://www.annalsofian.org/text.asp?2020/23/3/417/268676


Full Text



Sir,

Opercular syndrome (OPS) presents with bilateral paresis of facial, lingual, pharyngeal, and masticatory muscles innervated by 5th, 7th, 9th, 11th, and 12th cranial nerves leading to loss of voluntary control however the autonomic, involuntary and reflexive functions are intact. It occurs due to involvement of bilateral opercular area and vascular aetiology remains the most common leading to this syndrome. Herein, we are reporting a case presenting as trismus and later on diagnosed as opercular syndrome.

A 66-year-lady presented to emergency with acute onset inability to open mouth and speak. She was attended by emergency resident and evaluated for trismus. Neurology consultation was also sought as she had acute symptoms. She had acute onset trismus with tight closure of jaw, was unable to speak although she was conscious, alert, and obeying other commands. On examination she had subtle weakness of right upper limb. All cranial nerves could not be examined properly as she was not opening her mouth; however, later on after some improvement of trismus, she was found to have inability to move her tongue or swallow. However, it was noted that though she did not open her mouth on commands, but she was able to do so during smiling and yawning. She had blood pressure of 130/84 mm Hg and pulse of 84/min. MRI (Magnetic resonance imaging) brain showed acute infarct in left frontal opercular region [Figure 1]. CT angiography Brain was also unremarkable except paucity of the cortical branches of both middle cerebral arteries. Her routine investigations were normal except mild anemia with hemoglobin of 11.6 gm/dl. Electrocardiogram (ECG), echocardiogram and 24-hour Holter examination were normal. Lipid profile was normal. Serum CRP (C reactive protein) was 5.9 mg/dl. Vasculitis markers including ANA (antinuclear antibody), ANCA (antineutrophil cytoplasmic antibodies) were normal. She had history of type 2 diabetes and hypertension for 10 years. She was admitted in our hospital for ischemic stroke (infarction right frontal opercular region) 7 months back for which she was thrombolyzed with recombinant tissue plasminogen activator after which her weakness significantly improved and was regularly taking aspirin 150 mg since then. She was also diagnosed with adenocarcinoma right lung (on biopsy) 8 month back for which she was on regular chemotherapy (6 cycles of carboplatin and pemetrexed). After 2-month follow up, she was able to open her mouth to some extent but was not able to speak and was on Ryle's tube for feeding.{Figure 1}

Our patient presented with acute onset trismus, dysphagia and anarthria with subtle right upper limb weakness. She was able to open her mouth while yawning and laughing but was not able to do so on commands. This is the typical presentation of anterior opercular syndrome. Opercular syndrome is a rare type of cortical pseudobulbar palsy in which there is loss of voluntary innervation of the facio-pharyngo-glossomasticatory muscles with preservation of involuntary innervations.[1] There is bilateral paresis of facial, lingual, pharyngeal and masticatory muscles innervated by 5th, 7th, 9th, 11th, and 12th cranial nerves leading to loss of voluntary control; however, the autonomic, involuntary, and reflexive functions are intact.

Operculum is the area of brain cortex overlying insula, inferior frontal, inferior parietal, and superior temporal gyrus. In humans, there is both volitional and emotional control of facial and oral muscles. The volitional control requires primary motor cortex and pyramidal system whereas thalamus, hypothalamus, and extra pyramidal system are responsible for the spontaneous and emotional control.[2] This selective paralysis of voluntary muscles with preserved spontaneous and emotional function is called autonomic-voluntary dissociation and is characteristic feature of opercular syndrome. The aetiology includes stroke, multiple sclerosis, head trauma, tumor, acute disseminated encephalomyelitis, and neurodegenerative diseases with stroke being the commonest cause.

Opercular syndrome usually occurs with bilateral lesion; in our case patient had previous stroke in right frontal operculum 7 months back. However, she developed symptoms of opercular syndrome after the second stroke which involved left frontal opercular region.

Trismus is a condition of forced jaw closure due to spasm of masticatory muscles. The causes of trismus are medications related adverse effect (phenothiazines, neuropleptic, metoclopramide, amphetamine, methyphenidate, etc), infection like tetanus and rabies, local causes like oromandibular diseases, abscess, parotitis, tonsillitis, neoplasm (e.g. pharyngeal or parotid gland tumors) and radiotherapy for head and neck neoplasm. We also considered paraneoplastic syndrome as one of differentials as patient was having carcinoma of lung but the presentation and imaging finding was favoring the diagnosis of opercular syndrome.

In a study by Lund J on animals, an independent pattern generator in the brainstem was found to control chewing function and was modulated by afferent inputs from cortex and buccal mucosa, which was proven by the fact that chewing movement can occur by stimulation of buccal mucosa or corticobular neurons in a decerebrate cat.[3],[4] Automatic or involuntary system may act through independent pattern generator in brain stem and responsible for volitional control to the motor nucleus of muscles of mastication. In opercular syndrome, trismus is probably due to alteration in function of pattern generator leading to loss of voluntary control of chewing.[5] Trismus has been uncommonly described with anterior opercular syndrome.[6]

Physicians should be aware of this syndrome and its uncommon presentation with trismus for timely intervention particularly in case of acute stroke when there may not be obvious weakness of limbs.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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3Lund J. Evidence for a central neural pattern generator regulating the chewing cycle. In: Anderson D, Matthews B. editors. Mastication. Bristol: John Wright and Sons; 1976.
4Lai MM, Howard RS. Pseudobulbar palsy associated with trismus. Postgrad Med J 1994;70:823-4.
5Lai MM, Howard RS. Pseudobulbar palsy associated with trismus. Postgrad Med J 1994;70:823-4.
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