Unilateral Holmes tremor associated with compression of the brainstem by an ectatic vertebral artery
Shweta Prasad1, Vikram V Holla2, Dhruv Batra2, Pramod K. Pal2 1 Department of Clinical Neuroscience, National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru, Karnataka, India; Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru, Karnataka, India 2 Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru, Karnataka, India
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Correspondence Address: Dr. Pramod K. Pal Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru 560029, Karnataka. India
Source of Support: None, Conflict of Interest: None
Lesions affecting the Guillain–Mollaret triangle usually lead to palatal or oculopalatal tremors and occasionally Holmes tremors (HTs). We report two cases of unilateral HT without palatal tremor, secondary to brainstem compression by an ectatic vertebral artery. Unilateral HT may occur due to compression of the inferior olivary nucleus by an ectatic vertebral artery. This cause should be explored in patients who lack other obvious causes for tremor.
How to cite this article: Prasad S, Holla VV, Batra D, Pal PK. Unilateral Holmes tremor associated with compression of the brainstem by an ectatic vertebral artery. Ann Mov Disord 2020;3:56-9
How to cite this URL: Prasad S, Holla VV, Batra D, Pal PK. Unilateral Holmes tremor associated with compression of the brainstem by an ectatic vertebral artery. Ann Mov Disord [serial online] 2020 [cited 2022 Aug 12];3:56-9. Available from: https://www.aomd.in/text.asp?2020/3/1/56/281749
Holmes tremor (HT) is a low-frequency rest and action tremor occurring secondary to lesions involving the dentato-rubro-olivary pathway and dopaminergic nigrostriatal system. The dentato-rubro-olivary pathway commonly referred to as the Guillain–Mollaret triangle is composed of ipsilateral red nucleus, inferior olivary nucleus (ION), and contralateral dentate nucleus. Lesions affecting this are usually unilateral and occur secondary to demyelination, ischemia, and hemorrhage. Interruptions may lead to hypertrophic olivary degeneration (HOD) of the ION, and patients present with palatal or oculopalatal tremors and occasionally an HT. Direct injury to a component of this triangle is not a mandate to produce such symptoms. The occurrence of palatal myoclonus/tremor secondary to compression of the brainstem by an ectatic vertebral artery (VA) has been previously reported., Furthermore, occurrence of HT in the absence of palatal tremor has also been reported. These reports imply that external compression of the ION may produce symptoms akin to intrinsic damage, and in cases of HOD, that is, ION damage, HT can occur in isolation. This report describes two cases of unilateral HT, which was associated with compression of the brainstem by an ectatic VA.
A 25-year-old man presented with a 5-month history of right upper limb (UL) tremor and head tremor for 3 months. The UL tremor was predominantly observed with action and occasionally present at rest. The head tremor was an intermittent “no–no” tremor. There was no history of tremor elsewhere, and no other complaints. He had no other medical history or family history of tremor. On examination, there was a slight head tilt to the right, and minimal voice tremor on sustained phonation. He had a “no–no” type of head tremor with no obvious positional variations. At rest, there was a jerky tremor of the right UL [Video 1, Case 1]. Upon keeping the arms outstretched, dystonic posturing with a jerky tremor of the right hand was observed. A rubral tremor was observed when the right UL was flexed at the elbow and kept in front of the chest. There was no tremor of the left UL and both lower limbs. No palatal tremor was observed. There was minimal bradykinesia and positive Froment’s sign in the right UL. The rest of his examination was unremarkable. Magnetic resonance imaging (MRI) of brain [Figure 1], Case 1] showed an ectatic left VA compressing the anterolateral margin of the brainstem near the ION. There were no other abnormalities in the MRI, and all blood investigations were normal. Surface electromyography recordings from the right wrist extensors, wrist flexors, biceps, and triceps, when the arm was flexed in front of the chest, showed a 4–5 Hz tremor, suggestive of an HT [[Figure 2]. Video was taken after informed written consent.
Figure 1: Magnetic resonance images of the brainstem from both cases showing the presence of an ectatic vertebral artery (white arrow) compressing the anterolateral margin of the brainstem near the region of the inferior olivary nucleus. There is no evidence of hypertrophic olivary degeneration
Figure 2: Surface electromyography recordings for Case 1. Recordings obtained from the right wrist extensors, wrist flexors, biceps, and triceps, when the arm was flexed in front of the chest, showed a 4–5 Hz tremor, suggestive of a Holmes tremor
A 33-year-old man presented with a 2-year history of right UL tremor. The tremor was initially observed at rest and gradually observed with action. There was no history of tremor elsewhere or other complaints. He had no other medical history or family history of tremor. He had previously been diagnosed as Parkinson’s disease and was treated with pramipexole, rasagiline, and levodopa/carbidopa. He reported no improvement in symptoms with the above medication. On examination, he had mild hypomimia. At rest [Video 1, Case 2], there was a jerky tremor of the right UL. This was also present when the arms were kept outstretched; there was a rubral quality to the tremor when arms were flexed in front of the chest. In addition, there was mild dystonic posturing of the right hand when the hand was outstretched and flexed. The right UL tremor persisted while the patient was lying on the bed. There was no tremor in the left UL, both lower limbs and palate. There was grade 1 bradykinesia and rigidity in the right UL. There was slight reduction in the right arm swing. The rest of his examination was unremarkable. MRI brain [Figure 1], Case 2] showed an ectatic left VA compressing the anterolateral margin of the brainstem near the region of the ION. There were no other abnormalities in the MRI and all blood investigations were normal. Video was taken after informed written consent.
VA compression of the brainstem has been previously reported, and clinical features can be permanent or transient. Manifestations are predominantly vestibular, motor, or cerebellar deficits.[7 Although palatal tremor/myoclonus and HT have been reported in association with ischemic],[ hemorrhagic],[ or demyelinating insults of the ION],[ there are only two reports of palatal myoclonus arising secondary to compression from an ectatic VA in the absence of HOD., HT secondary to the compression of the ION by an ectatic VA has not been reported before.
The ION is the main source for climbing fibers and is one of two main afferent pathways in the cerebellum. Disruption of this excitatory pathway will lead to an overall reduction in the inhibitory function of the cerebellum as the Purkinje cells will be inadequately activated to produce an inhibitory output [Figure 3]. This may lead to excessive activation of the thalamus and consequently increased activation of normal oscillatory networks, and this may contribute to the production of tremor. Absence of HOD in our cases may be due to the fact that only pathologies that affect afferent fibers, that is, dentato-rubral or rubro-olivary pathway, lead to development of HOD. HOD occurs due to deafferentation of the ION, and in this report, there were no abnormalities in the afferent tracts. Palatal tremor is suggested to be secondary to abnormalities in the central tegmental tract, that is, the rubro-olivary pathway. Absence of palatal tremor in this report may be due to the lack of abnormality in this tract.
Figure 3: Schematic representation of the Guillain–Mollaret triangle and main cerebellar afferents. HOD = hypertrophic olivary degeneration, ICP = inferior cerebellar peduncle, SCP = superior cerebellar peduncle
Medical management of such tremors may be unsatisfactory. Microvascular decompression (MVD) has been attempted with variable results. Deep brain stimulation (DBS) of the ventral intermediate (VIM) nucleus may have promising outcomes.
In conclusion, a unilateral HT may occur due to compression of the ION by an ectatic VA. This cause should be explored in patients who lack other obvious causes for tremor. MVD may not necessarily benefit such patients and VIM DBS should be considered.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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