“SILENT”: A case report of a rare syndromal presentation of chronic lithium toxicity

ABSTRACT

This text discusses a case report of an affected person with bipolar ailment who developed the syndrome of irreversible lithium effectuated neurotoxicity (SILENT). In this case of a 62-year-old man with bipolar affective disorder, we found how continual lithium therapy can position a patient requiring chronic mood stabilizer treatment vulnerable to developing the silent syndrome. The case presentation covered a set of symptoms inclusive of encephalopathy, cerebellar dysfunction, stress, and limb tremors at the time of admission. A serial neurological examination and mental status examination for ascertaining the diagnosis of the silent syndrome were carried out, and the affected person was advised to discontinue lithium and was handled symptomatically for other symptoms. We ought to identify and manage the hazard elements contributing to the development of this syndrome.

Lithium stays the primary line of treatment for bipolar disorder. Because of the narrow therapeutic index, lithium toxicity is frequently encountered. Lithium-induced neurotoxicity can be irreversible and possibly life-threatening.[1] Acute lithium toxicity can also present with ataxia, coarse tremors, dyskinesias, dysarthria, hyperreflexia, and myopathy. In extreme cases, seizures or acute confusion state can also occur.[2] SILENT, which stands for ‘Syndrome of irreversible lithium effectuated neurotoxicity’, has been described as neurological signs and symptoms of lithium toxicity that persists for a period of minimum 2 months after stopping the drug in patients without any past history of neurological illness.[3] There is scarcity of literature dealing with SILENT syndrome, especially within the Indian context, and as there may be a constant increase in mentioned cases worldwide, specifically with co-morbid psychiatric illness, further studies in this direction are warranted. Here, we report a rare case of SILENT in a 62-year-old male from South India.

CASE HISTORY

Mr. M was a 62-year-old unmarried male who belonged to the lower socio-economic strata. He was diagnosed with bipolar affective disorder and was maintaining well on Tablet Lithium in doses ranging from 600 to 1200 mg per day as a mood stabilizer for 30 years. Approximately 6 months ago, the patient had developed pain in the lower extremities, which worsened over the next 2 months to the extent to which the patient had difficulty walking and would be seen walking with short steps. He also started experiencing coarse tremors in both upper and lower extremities that impaired his routine tasks and daily functioning. Following this, the patient was evaluated by the family physician, who advised the patient to discontinue the tablet Lithium but did not provide a reason for the same.

Despite stopping lithium, over the next few weeks, the patient’s tremors and weakness increased to the extent that he would have difficulty getting up from the sitting position. He also experienced difficulty in executing activities of daily living, requiring assistance for most activities including mobilizing and feeding himself. The patient additionally had trouble with speech and often stuttered and repeated phrases time and again. He would speak incoherently, and speech was incomprehensible to his own family. According to family members, the patient would not provide appropriate answers to any questions and was unable to follow simple commands. He would appear perplexed and confused for most of the day and would not be able to sleep at night. Every now and then, the patient was seen restless and shouting out names of relatives who were not living in the house. Subsequently, he also suffered a fall, after which the patient’s pain and distress increased, and he became bedridden for 15 days before being taken to the emergency department for further evaluation.

Upon admission, the patient was evaluated and in-depth neurological examination was performed, which revealed acute encephalopathy characterized by an altered mental state; disorientation to time, place, and person along with marked fluctuation in consciousness; and a Mini-Mental Score Examination (MMSE) score of 13/30. He additionally had tremors that were more pronounced in upper extremity than lower extremity along with intense dysarthria, postural instability, and cogwheel rigidity that was more in the upper extremity than lower extremity. The affected person additionally had preserved upper limb reflexes and exaggerated lower limb reflexes along with bilaterally reduced power in upper and lower limbs. Investigations performed included routine serum investigations which were within normal limits and serum lithium levels that were 1.5 mEq/L at that point. Magnetic resonance imaging of the brain was performed, which revealed small vessel ischemic changes and age-related cortical atrophy [Figure 1] and hyper-intensities in frontal and parietal lobes on t2 flair [Figure 2]. The patient was then diagnosed with SILENT syndrome, following which the need for psychotropic drugs was reassessed. The patient was then managed only with tablet Quetiapine 100 mg and Lorazepam 2 mg.

Figure 1.

Age-related cortical atrophy

Figure 2.

Hyper-intensities on T2 Flair

Serial examinations performed to evaluate the severity and progression discovered an improvement in all of the above symptoms and signs within 7 days of admission. The patient’s family was psycho-educated about the situation and informed that the condition may sufficiently improve over the years after lithium withdrawal and they needed to re-consider optimizing psychiatric medication in the future to prevent relapse of mood symptoms. The patient was then discharged and advised regular follow-ups.

Following a 2-month follow-up period, the patient was re-assessed for severity and progression of symptoms. He was found to be fully oriented with an intact sensorium and an MMSE score of 27/30. In addition, no active manic or depressive symptoms were noted. The patient however continued to have dysarthria and minimal tremors of upper and lower limbs, although not limiting his daily activities. The patient could mobilize and walk in a short shuffling-type gait and would be able to carry out activities of everyday living with little to no help from his family members. He was also regularly taking tab. Quetiapine 100 mg and Lorazepam 2 mg and was advised to continue the same and encouraged to keep coming for follow-up in the future.

DISCUSSION

Chronic pharmacotherapy with lithium often causes increased levels in the brain because of physiological accumulation over time leading to demyelination, which causes encephalopathy like the picture. The syndrome can also present with other symptoms like persistent cerebellar dysfunction, persistent extrapyramidal syndrome, persistent brainstem dysfunction, or dementia with varying organic mental syndromes.[3,4] It also sometimes presents in an atypical manner which includes downbeat nystagmus, retrobulbar optic neuritis, persistent papilledema, choreoathetosis movements, peripheral neuropathy, myopathy, and blindness.[4]

In the present case, we observed how chronic therapy with lithium can put a patient needing a chronic mood stabilizer for a mood disorder at risk of developing SILENT syndrome. In this particular case, the presentation included a typical set of symptoms and was appropriately advised to stop lithium and was symptomatically managed for other complaints.

CONCLUSION

There is no doubt in the fact that lithium was, and is being, used as a first-line treatment for bipolar disorder because of its efficacy as a mood stabilizer.[5] However, as observed clinically, it poses serious threats of toxicity which can present both acutely and chronic Although the acute presentation can be managed adequately with minimal to nil post-treatment sequelae, it is, however, the chronic toxicity that occurs because of prolonged accumulation in the brain parenchyma. The affected person thus presents with an array of debilitating neurological and psychiatric symptomatology. Hence, it becomes necessary for us as clinicians to ensure and promote regular monitoring of serum lithium levels in patients on chronic pharmacotherapy and to watch out for signs of lithium toxicity including other symptoms of SILENT syndrome mentioned above.

Declaration of patient consent

Patient has given his consent to be included in the case report. The patient has agreed to provide his clinical details and for the same to be reported in the journal. The patient understands that his name and personal details will not be divulged, and his identity will be concealed, however absolute anonymity was not guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.