Serotonin Syndrome complicates into PRES, A rare case scenario

A young male receiving serotonergic agents presented with symptoms suggestive of serotonin syndrome including severe dysautonomia leading to PRES (a very rare finding). He was successfully treated with 5-HT2 antagonistic agent.

Dr. Sanjay Prakash et al currently working in Neurology, Smt. BK Shah Medical Institute and Research Centre, Sumandeep Vidyapeeth, Waghodia, Gujarat, India, published a case study in British Medical Journal (BMJ), regarding this rare abnormality occurring in SS.

SS is characterised by triad of [1] cognitive impairment (ranging from mild irritability to coma),[2] autonomic hyperactivity, and [3] neuromuscular abnormalities. However, severe dysautonomia may occur in some patients, leading to hypertensive crisis, posterior reversible encephalopathy syndrome (PRES), myocardial infarction and even death.

A 37-year-old man presented with history of chronic tension-type headache and depression for 4-5 months for which he had been taking amitriptyline which was gradually increased to a dose up to 50mg/day. After obtaining no relief paroxetine was added and was titrated up to 25mg/day. 2 days after increasing paroxetine patient experienced generalised body pains associated with irritability and transient visual obscuration, however, he continued with the drugs. Later there was unsteadiness in gait followed by tremulousness all over, including limbs. Symptoms gradually worsened and he developed slurred speech, fever and diaphoresis, after which patient was then brought to Emergency Department while he was agitated and incomprehensible.

General physical examination revealed- high temperature-100.8⁰F, tachycardia-110bpm, hypertension-176/94mmHg, and tachypnea. No h/o hypertension or any other illness was present. Systemic examination was normal, while on neurological examination, patient was alert but agitated and speech was incomprehensible. Cranial nerve examination was normal including optic disc. Detailed motor examinations revealed coarse postural tremor, generalised hypertonia, brisk deep tendon reflex, inducible clonus at the ankles and knees, extensor plantar response, and incoordination in both upper and lower limbs. The patient was suspected of having SS, and the clinical features fulfilled the Hunter criteria of SS. As SS is considered as a medical emergency, cyproheptadine and clonazepam had been started immediately, and amitriptyline and paroxetine were discontinued. All biochemical and haematological investigations were normal except TLC which was- 12,900mm^3. ECG showed tachycardia. MRI performed on day 2 showed hyper intense signals in occipital, partial, temporal and cerebellum lobes suggestive of PRES.

PRES is a clinical syndrome with 3 key components:- (a) acute neurological features, (b) specific Neuroimaging findings, (c) obvious risk factors. PRES is typically characterised by vasogenic oedema without infarction, involving predominantly bilateral subcortical areas of the parietal and occipital lobes. It typically presents in patients with acute hypertensive disorders.

However, differential diagnosis of viral encephalitis, acute disseminated encephalomyelitis and posterior circular stroke were also considered. But, investigation for same ruled out the possibility, furthermore, prompt response to cyproheptadine (for SS) excluded other secondary possibilities.

Patient was treated with 12mg loading dose of cyproheptadine administered immediately along with supportive care, followed by 2mg every 2hrs. Clonazepam was started at 0.5mg twice daily.

8 hrs after the therapy, patient was not agitated and speech was comprehensible. HR, BP and temperature were normal within 24 hours. On 2nd day there was no diaphoresis, tremulousness, myoclonus or clonus. While hypertonia and hyperreflexia disappeared in 2–3 days, incoordination resolved in 5–6 days. Cyproheptadine was gradually tapered and discontinued after 2 weeks. There was no recurrence of symptoms, including hypertension, during the 9-month follow-up. A follow-up MRI of the brain performed after 2 months revealed no abnormalities. Visual disturbance and incoordination may be predominantly because of PRES.

PRES was not a working diagnosis. It was revealed on MRI. As patient was treated for SS most symptoms disappeared.

SS typically resolves within 24 hours after the initiation of therapy. SS is a highly underdiagnosed clinical condition. The co-occurrence of PRES and SS is unusual and can easily escape recognition, especially if the patient is not subjected to neuroimaging (MRI brain), which is not usually advised in patients with SS.

Source: British Medical Journal: Prakash S, Rathore C, Kaushikkumar R. Posterior reversible encephalopathy syndrome in a patient with serotonin syndrome. BMJ Case Rep. 2020 Dec 9;13(12):e236450. doi: 10.1136/bcr-2020-236450.