Anismus-A Very Unusual Extrapyramidal Side Effect of Paliperidone Palmitate in an Adolescent with Schizo-Affective Disorder

Abstract

Here, authors report on an interesting case of an adolescent with a diagnosis of schizo-affective disorder, maintained on LAI paliperidone palmitate that developed an unusual dystonic reaction in form of anismus that masquerade as constipation and faecal impaction. To our knowledge, this is one of the earliest reports of antipsychotic-induced anismus notably in adolescent population. Clinicians should be mindful of unusual forms of dyskinesias that might be associated with high-potency antipsychotic use.

Case Vignette

We were called upon to see a 16-year-old male Bahraini adolescent, a known case of schizo-affective disorder, maintained on paliperidone palimitate 100 mg IM q 4 weeks for poor compliance and repeated hospitalizations in the past. He was in partial remission but recently admitted on surgical wards for recurrent constipation and faecal impaction. Extensive medical workup was negative. Anorectal manometry, baloon expulsion and MRI proctography were undertaken and a tentative diagnosis of anismus was entertained by surgical team. Team wondered whether or not antipsychotic treatment could be contributory and the practicality of switching if this would be the case. As the patient has been trialled previously on aripiprazole and olanzapine with poor response, we were a bit reluctant to sacrifice his therapeutic response to paliperidone. Digging more into history of constipation, a temporal association was noted as paliperidone dose went up from 6 mg to 9 mg/d. At this dose, chart review showed that patient has attended ER on two occasions with oculogyric crises that responded favourably to STAT orphenadrine 60 mg IM. Neurological examination revealed bilateral appendicular rigidity. At this point, one of our CL team (A.N.) hypothesized anismus could be a form of paliperidone-induced dystonia. To put this to test, we split over decrease paliperidone palmitate down to 75 mg IM q 4 wks on next due, which could jeopardize treatment response, or else, paradoxically, add an anticholinergic agent (ACA), procyclidine, which could otherwise worsen constipation. We opted finally to go with latter choice of introducing an ACA, low and slow, since patient is closely monitored on surgical bay. To our surprise, over three days only, on 2.5 mg/d (on 2 doses), bowel movements improved, and rigidity as well. Three months elapsed at the time of writing this report, and patient is maintained on same treatment regimen, mentally stable, and above all, with no incidents of constipation, tenesmus, faecal impaction or encopresis.

Discussion

Anismus (aka puborectalis syndrome), is paradoxical contraction of the external anal sphincter during attempted defaecation, leading to faecal retention and a complaint of constipation.¹ This could be idiopathic and occurs in isolation, or as an ‘off’ phenomenon in Parkinson’s disease.² It is thought to represent a focal dystonia,³ and may be helped temporarily by local injections of botulinum toxin. We failed to locate any case reports related to antipsychotic use. Our report remains one of the earliest to report on paliperidone-related anismus as acute dystonic reaction (ADR) due to potent D₂ blockade in the nigro-striatal pathway (projections from substantia nigra pars compacta to posterior parts of caudate and putamen) with resultant alteration in dopamine to acetylcholine ratio at basal ganglia level.⁴ Moreover, response of anismus to ACA is quite novel, albeit sounds counter-intuitive. A limitation that we do acknowledge in this report is the Challenge-Dechallege-Rechallenge design that could be more conclusive was not feasible due to ethical concerns.

Anti-psychotic-induced ADRs are commonly seen with high-potency conventional antipsychotics. Risk factors include young age, male gender, history of drug-induced dystonia, recent cocaine use, hypocalcaemia, hypoparathyroidism, and dehydration.⁵ ADRs can be anywhere in the body and vary in manifestation but generally readily and clinically obvious. Most common locations are in the head and neck regions. Different forms of focal dystonias related to antipsychotic use have been described including, inter alia, oculogyric crisis, torticollis, opisthotonos, pseudomacroglossia, tortipelvic crisis, trismus, dysarthria and potentially life-threatening laryngospasm. Similarly, we have previously reported on aripiprazole-induced stuttering⁶ and lithium-induced Ekbom’s syndrome.⁷

It behoves clinicians to be vigilant to hidden and lesser known semiology of extrapyramidal syndromes especially when using high-potency or first generation antipsychotics.