Hypertrophic olivary degeneration
Updates to Article Attributes
Hypertrophic olivary degeneration (HOD) is is a rare condition characterised by a unique pattern of trans-synaptic degeneration. Typically Typically it is caused by a lesion in the brainstem/cerebellum interrupting the triangle of Guillain and Mollaret, resulting in hypertrophy of the inferior olivary nucleus.
It should be noted, however, that in a significant proportion of patients no causative lesion will be identified 5.
Clinical presentation
Oculopalatal tremor is a distinctive part of the presentation of hypertrophic olivary degeneration, although is also seen in many other brainstem and cerebellar conditions 4. Oculopalatal Oculopalatal tremor comprises ocular, palatal and other muscular involuntary movements7,8.
-
palatal myoclonus (symptomatic palatal myoclonus) 7,8
rhythmic 1-3 Hz involuntary movement of the soft palate and uvula potentially extending to involve the pharynx and larynx
may persist during sleep
not always be present, but when it is present, it is pathognomonic
oscillopsia
maymay be present due to the pendular nystagmus caused by the oculartremormyoclonus 4,8upper extremity tremor (Holmes tremor) may also be present 4,8
facial, cervical, intercostal, and diaphragmatic myoclonus may also be present 7,8
Pathology
The connection between the red nucleus, ipsilateral inferior olivary nucleus and the contralateral dentate nucleus forms the triangle of Guillain and Mollaret. Interruption Interruption of either connection between the dentate nucleus and contralateral red nucleus (dentatorubral tract, superior cerebellar peduncle) or the connection between the red nucleus and ipsilateral inferior olivary nucleus (central tegmental tract) leads to changes in the olive. The olive receives inhibitory (GABAergic) signals within the dentato-rubro-olivary pathway, with transneuronal degeneration causing enlargement rather than atrophy.
Pathologically, this is characterised by "trans-synaptic degeneration resulting in vacuolation of the neurones" and an increase in astrocytes. Isolated lesions of the inferior cerebellar peduncle do not cause hypertrophic olivary degeneration, as anatomically there are no direct connections between the inferior olivary nucleus and the contralateral dentate nucleus (fibres from the inferior olivary nucleus project to the cerebellar cortex via the olivocerebellar tracts and then to the dentate nucleus).
Oculopalatal tremor results from disinhibition of the inferior olivary nucleus, following the pathology in dentato-rubro-olivary pathway which is further modulated by the cerebellum 4.
Radiographic features
Hypertrophic olivary degeneration is often seen several months after the original insult.
MRI
The inferior olivary nucleus gets larger and increases in signal intensity on T2 weighted and T2-FLAIR sequences.
Typically, within a few months, T2 signal increases and lasts for 3-4 years, whereas hypertrophy occurs later (at about one year), and resolves by 3-4 years. There are three stages:
T2 hyperintense without olivary swelling
T2 hyperintense and olivary swelling occur concomitantly, developing after 6 months and persisting for nearly 3-4 years
olivary swelling subsides, but T2 hyperintensity persists
The ipsilateral red nucleus may lose the expected normal hypointensity on SWI 6.
Treatment and prognosis
Management is primarily directed towards the underlying cause 9. Otherwise, pharmacological symptomatic treatment of oculopalatal myoclonus secondary (e.g. sodium valproate, clonazepam) tends to not be successful 8,9.
Differential diagnosis
General imaging differential considerations include:
infarction
metastases
lymphoma
infection, including tuberculosis
Clinical differential considerations include:
essential palatal myoclonus
-<p><strong>Hypertrophic olivary degeneration (HOD)</strong> is a rare condition characterised by a unique pattern of trans-synaptic degeneration. Typically it is caused by a lesion in the brainstem/cerebellum interrupting the <a href="/articles/triangle-of-guillain-and-mollaret">triangle of Guillain and Mollaret</a>, resulting in hypertrophy of the <a href="/articles/inferior-olivary-nucleus">inferior olivary nucleus</a>.</p><p>It should be noted, however, that in a significant proportion of patients no causative lesion will be identified <sup>5</sup>.</p><h4>Clinical presentation</h4><p>Oculopalatal tremor is a distinctive part of the presentation of hypertrophic olivary degeneration, although is also seen in many other brainstem and cerebellar conditions <sup>4</sup>. Oculopalatal tremor comprises ocular, palatal and other muscular involuntary movements.</p><ul>- +<p><strong>Hypertrophic olivary degeneration (HOD)</strong> is a rare condition characterised by a unique pattern of trans-synaptic degeneration. Typically it is caused by a lesion in the brainstem/cerebellum interrupting the <a href="/articles/triangle-of-guillain-and-mollaret">triangle of Guillain and Mollaret</a>, resulting in hypertrophy of the <a href="/articles/inferior-olivary-nucleus">inferior olivary nucleus</a>.</p><p>It should be noted, however, that in a significant proportion of patients no causative lesion will be identified <sup>5</sup>.</p><h4>Clinical presentation</h4><p>Oculopalatal tremor is a distinctive part of the presentation of hypertrophic olivary degeneration, although is also seen in many other brainstem and cerebellar conditions <sup>4</sup>. Oculopalatal tremor comprises ocular, palatal and other muscular involuntary movements <sup>7,8</sup>.</p><ul>
-<p>palatal myoclonus</p>- +<p>palatal myoclonus (symptomatic palatal myoclonus) <sup>7,8</sup></p>
-<li><p>rhythmic involuntary movement of the soft palate and uvula potentially extending to involve the pharynx and larynx</p></li>- +<li><p>rhythmic 1-3 Hz involuntary movement of the soft palate and uvula potentially extending to involve the pharynx and larynx</p></li>
- +<li><p>may persist during sleep</p></li>
-<li><p><a href="/articles/oscillopsia" title="Oscillopsia">oscillopsia</a> may be present due to the pendular nystagmus caused by the ocular tremor <sup>4</sup></p></li>-<li><p>upper extremity tremor may also be present <sup>4</sup></p></li>-</ul><h4>Pathology</h4><p>The connection between the red nucleus, ipsilateral inferior olivary nucleus and the contralateral dentate nucleus forms the triangle of Guillain and Mollaret. Interruption of either connection between the dentate nucleus and contralateral red nucleus (<a href="/articles/dentatorubral-tract">dentatorubral tract</a>, <a href="/articles/superior-cerebellar-peduncle-1">superior cerebellar peduncle</a>) or the connection between the red nucleus and ipsilateral inferior olivary nucleus (central <a href="/articles/tegmental-tract">tegmental tract</a>) leads to changes in the <a href="/articles/olive">olive</a>. The olive receives inhibitory (GABAergic) signals within the dentato-rubro-olivary pathway, with transneuronal degeneration causing enlargement rather than atrophy. </p><p>Pathologically, this is characterised by "trans-synaptic degeneration resulting in vacuolation of the neurones" and an increase in astrocytes. Isolated lesions of the inferior cerebellar peduncle do not cause hypertrophic olivary degeneration, as anatomically there are no direct connections between the inferior olivary nucleus and the contralateral dentate nucleus (fibres from the inferior olivary nucleus project to the cerebellar cortex via the <a href="/articles/olivocerebellar-tract">olivocerebellar tracts</a> and then to the dentate nucleus). </p><p>Oculopalatal tremor results from disinhibition of the inferior olivary nucleus, following the pathology in dentato-rubro-olivary pathway which is further modulated by the cerebellum <sup>4</sup>. </p><h4>Radiographic features</h4><p>Hypertrophic olivary degeneration is often seen several months after the original insult.</p><h5>MRI</h5><p>The inferior olivary nucleus gets larger and increases in signal intensity on T2 weighted and T2-FLAIR sequences.</p><p>Typically, within a few months, T2 signal increases and lasts for 3-4 years, whereas hypertrophy occurs later (at about one year), and resolves by 3-4 years. There are three stages:</p><ol>- +<li><p><a href="/articles/oscillopsia" title="Oscillopsia">oscillopsia</a> may be present due to the pendular nystagmus caused by the ocular myoclonus <sup>4,8</sup></p></li>
- +<li><p>upper extremity tremor (Holmes tremor) may also be present <sup>4,8</sup></p></li>
- +<li><p>facial, cervical, intercostal, and diaphragmatic myoclonus may also be present <sup>7,8</sup></p></li>
- +</ul><h4>Pathology</h4><p>The connection between the red nucleus, ipsilateral inferior olivary nucleus and the contralateral dentate nucleus forms the triangle of Guillain and Mollaret. Interruption of either connection between the dentate nucleus and contralateral red nucleus (<a href="/articles/dentatorubral-tract">dentatorubral tract</a>, <a href="/articles/superior-cerebellar-peduncle-1">superior cerebellar peduncle</a>) or the connection between the red nucleus and ipsilateral inferior olivary nucleus (central <a href="/articles/tegmental-tract">tegmental tract</a>) leads to changes in the <a href="/articles/olive">olive</a>. The olive receives inhibitory (GABAergic) signals within the dentato-rubro-olivary pathway, with transneuronal degeneration causing enlargement rather than atrophy. </p><p>Pathologically, this is characterised by "trans-synaptic degeneration resulting in vacuolation of the neurones" and an increase in astrocytes. Isolated lesions of the inferior cerebellar peduncle do not cause hypertrophic olivary degeneration, as anatomically there are no direct connections between the inferior olivary nucleus and the contralateral dentate nucleus (fibres from the inferior olivary nucleus project to the cerebellar cortex via the <a href="/articles/olivocerebellar-tract">olivocerebellar tracts</a> and then to the dentate nucleus). </p><p>Oculopalatal tremor results from disinhibition of the inferior olivary nucleus, following the pathology in dentato-rubro-olivary pathway which is further modulated by the cerebellum <sup>4</sup>. </p><h4>Radiographic features</h4><p>Hypertrophic olivary degeneration is often seen several months after the original insult.</p><h5>MRI</h5><p>The inferior olivary nucleus gets larger and increases in signal intensity on T2 weighted and T2-FLAIR sequences.</p><p>Typically, within a few months, T2 signal increases and lasts for 3-4 years, whereas hypertrophy occurs later (at about one year), and resolves by 3-4 years. There are three stages:</p><ol>
-</ol><p>The ipsilateral red nucleus may lose the expected normal hypointensity on SWI <sup>6</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>- +</ol><p>The ipsilateral red nucleus may lose the expected normal hypointensity on SWI <sup>6</sup>.</p><h4>Treatment and prognosis</h4><p>Management is primarily directed towards the underlying cause <sup>9</sup>. Otherwise, pharmacological symptomatic treatment of oculopalatal myoclonus secondary (e.g. sodium valproate, clonazepam) tends to not be successful <sup>8,9</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>
-</ul>- +</ul><p>Clinical differential considerations include:</p><ul><li><p>essential palatal myoclonus</p></li></ul>
References changed:
- 7. Jankovic J, Hallett M, Okun MS, et al. Principles and Practice of Movement Disorders. (2021) ISBN: 9780323310710 - <a href="http://books.google.com/books?vid=ISBN9780323310710">Google Books</a>
- 8. Wang H, Wang Y, Wang R et al. Hypertrophic Olivary Degeneration: A Comprehensive Review Focusing on Etiology. Brain Res. 2019;1718:53-63. <a href="https://doi.org/10.1016/j.brainres.2019.04.024">doi:10.1016/j.brainres.2019.04.024</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/31026459">Pubmed</a>
- 9. Bhattacharjee S. Palatal Tremor - Pathophysiology, Clinical Features, Investigations, Management and Future Challenges. Tremor Other Hyperkinet Mov (N Y). 2020;10(1):40. <a href="https://doi.org/10.5334/tohm.188">doi:10.5334/tohm.188</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/33101766">Pubmed</a>