This image was created by Andrew Gillies and is licensed under the Creative Commons Attribution Share-Alike 3.0 License. See here for further details. GPe – External Globus Pallidus GPi Internal Globus Pallidus STN Subthalamic Nucleus SN Substantia Nigra
The article reviewed here is a brief letter titled ‘Catatonic Stupor in a Case of Pontine and Extrapontine Myelinolysis: Clinical and Radiological Dissociation’ by Miyares and colleagues and freely available here. The authors describe a 23-year old man who presented with confusion, a stuporose state and that
‘During passive movements the limb was kept in the same position for a prolonged period even when the position and posture seemed uncomfortable and bizarre‘
This is a phenomenon also referred to as waxy flexibility. What’s interesting here is that the authors have identified neuropathology from the imaging investigations. Thus there were slow waves on the EEG and on the MRI they have identified T2 weighted hyperintense signals in two regions – the Pons and the Basal Ganglia (the Basal Ganglia are illustrated above in coronal section). Thus in conjunction with the clinical features they conclude that there is Pontine and Extrapontine Myelinolysis. He was treated with Risperidone and improved even though the hyperintense lesions remained.
I thought there were two interesting features here – the association with compulsive eating and the association with Pontine and Extrapontine Myelinolysis. In the draft version of DSM-V, consideration is being given to adding a catatonia specifier to the diagnosis of schizophrenia so that it’s presence or absence would be explicitly stated (see here). Catatonia can manifest in a number of different ways and there are most likely many different causes. In this case, the association of involvement of the Basal Ganglia with waxy flexibility is plausible but on the basis of a single case alone it is not possible to draw any firm conclusions.
A superficial examination of the literature using the Medline database (via PubMedNet) and using the keywords ‘Pontine Myelinolysis’ produces 777 results from 1959-2010 inclusive. A cursory inspection of the most recent abstracts reveals associations including a rapid correction of hyponatraemia (Mastrangelo et al, 2009)(Hawthorne et al, 2009), hypokalaemic nephrogenic diabetes insipidus (Davenport et al, 2010) and rapid correction of hyperammonaemia (Langer et al, 2010) amongst others (there were also cases associated with slowly corrected hyponatraemia, following liver transplantation, surgery for a craniopharnygioma as well as gestational diabetes). The association between a rapid correction of sodium levels and ‘osmotic demyelination’ or ‘pontine myelinolysis’ was emphasised by a number of the authors. Indeed the authors of this case study noted that the sodium levels as well as other urea and electrolytes were within normal limits on the current admission. However during an earlier admission they note that there was hyponatraemia and that this was corrected. Thus there is a possible explanation that encompasses the initial presentation with hyponatraemia through to the development of catatonia with waxy flexibility. It possible to speculate that compulsive eating may have influenced the rate of correction of hyponatraemia.
Is there A Relationship Between Pontine Myelinolysis and Neuroleptic Malignant Syndrome?
In an effort to triangulate these results with catatonia. I used the terms ‘catatonia’ and ‘sodium’ for the same years and database but produced only 19 results which didn’t seem too interesting apart from the use of ‘dantrolene sodium’ for catatonia and also the consideration of ‘malignant catatonia’ better known as the Neuroleptic Malignant Syndrome. Could there be cases of Pontine Myelinolysis which result in NMS? Surprisingly the answer is yes. There were two papers identified by searching the same database/years using the terms ‘Pontine Myelinolysis’ and ‘Neuroleptic Malignant Syndrome’ produces one paper in english (Groff et al, 2005) and another in spanish (González et al, 2010). The spanish authors comment in the title on the similarity of the Pontine Myelinolysis presentation with that of NMS while the authors of the other paper note the development of pontine myelinolysis after NMS.
Case reports offer a useful starting point for asking useful clinical questions and starting a line of inquiry in response to those questions. If the DSM-V draft changes come to pass then catatonia will be considered more explicitly and may become a more prominent term in the literature meaning that case studies like this might become more frequent. Searches through medline produce potentially useful findings or associations. For instance one of the papers identified in the searches was about an 11-year old boy who had Pontine Tegmental lesions and who developed auditory and visual hallucinations (Vita et al, 2008). The authors of that study speculated that the lesions were interfering with REM sleep and that the hallucinations were in effect a phenomenon that should have been experienced in REM sleep rather than awake in the waking state (the hallucinations involved Harry Potter). Interestingly there is another condition where REM sleep mechanisms have been invoked as causal explanations of hallucinations – Lewy Body Dementia which affects both subcortical and cortical regions.
In summary, pontine and extrapontine myelinolysis in this case was associated with catatonia. There is another case described above in which a pontine lesion was associated with visual and auditory hallucinations and may be a useful differential in psychosis. There were some experimental papers on treatment (including returning to the hyponatraemia state in an animal model and some suggestions by a Chinese group including the use of gamma globulins). As in the case report, treatment of Pontine/Extrapontine Myelinolysis would be managed by the neurologists and it is interesting to see how there is a potential for useful interdisciplinary discussion in areas such as this.
Davenport C, Liew A, Vic Lau P, Smith D, Thompson CJ, Kearns G, Agha A. Ann Clin Biochem. 2010 Jan;47(Pt 1):86-9. Epub 2009 Nov 25. Central pontine myelinolysis secondary to hypokalaemic nephrogenic diabetes insipidus.
González Robledo J, Ballesteros Herráez JC, Chamorro Fernández A, Martín Polo J. Med Intensiva. 2007 Aug-Sep;31(6):342-3. [Central pontine myelinolysis after malignant neuroleptic syndrome][Article in Spanish]
Groff KE, Lam C, Caroff SN. J Clin Psychopharmacol. 2005 Dec;25(6):620-1. Extrapontine myelinolysis resembling neuroleptic malignant syndrome.
Hawthorne KM, Compton CJ, Vaphiades MS, Roberson GH, Kline LB. J Neuroophthalmol. 2009 Dec;29(4):296-9. Ocular motor and imaging abnormalities of midbrain dysfunction in osmotic demyelination syndrome.
Langer JE, Wilson WG, Raghavan P, Rust RS, Goodkin HP. Pediatr Neurol. 2010 Feb;42(2):154-6. Extrapontine myelinolysis resulting in transient cortical blindness.
Mastrangelo S, Arlotta A, Cefalo MG, Maurizi P, Cianfoni A, Riccardi R. Neuropediatrics. 2009 Jun;40(3):144-7. Epub 2009 Dec 17. Central pontine and extrapontine myelinolysis in a pediatric patient following rapid correction of hypernatremia.
Vita MG, Batocchi AP, Dittoni S, Losurdo A, Cianfoni A, Stefanini MC, Vollono C, Della Marca G, Mariotti P. J Clin Sleep Med. 2008 Dec 15;4(6):588-90. Visual hallucinations and pontine demyelination in a child: possible REM dissociation?
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