In a 58‑year‑old man with bipolar affective disorder who fell four months ago, had a subdural hematoma evacuated via burr‑hole one month ago, and now presents with persistent irritability, reduced sleep and recent urinary incontinence, what are the most likely causes and what immediate investigations and management should be undertaken?

Post-Burr Hole Subdural Hematoma with Persistent Irritability and New Urinary Incontinence

Immediate Differential Diagnosis and Most Likely Causes

The most likely causes are recurrent or residual subdural hematoma, normal pressure hydrocephalus (NPH), or delirium from an underlying medical condition—all of which require urgent neuroimaging and medical workup. 1

Primary Diagnostic Considerations

• Recurrent or residual subdural hematoma is the leading concern given the recent burr hole procedure (1 month ago), persistent irritability since the initial fall (4 months ago), and new urinary incontinence 2, 3
• Chronic subdural hematoma commonly presents with psychiatric symptoms including irritability, cognitive changes, and behavioral disturbances, particularly in patients with pre-existing psychiatric conditions like bipolar disorder 3, 4
• Post-operative subdural fluid collections with mass effect are associated with persistent psychiatric symptoms, especially in older patients (this patient is 58 years old) 3
• Normal pressure hydrocephalus (NPH) must be considered given the classic triad component of urinary incontinence appearing after neurosurgical intervention 1

Secondary Considerations

• Delirium from metabolic derangement, infection, or medication effects given the acute change in urinary continence 1
• Bipolar disorder exacerbation or mood episode, though less likely to cause urinary incontinence without neurological cause 5, 6
• Medication-related urinary retention with overflow incontinence, particularly if the patient is on anticholinergic medications 1, 7

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Immediate Investigations Required

Urgent Neuroimaging (Within 24 Hours)

• Non-contrast CT head immediately to assess for recurrent subdural hematoma, residual collection, hydrocephalus, or new intracranial pathology 1, 3
• If CT shows subdural fluid collection or hydrocephalus, MRI brain with and without contrast provides superior detail of subdural membranes, brain parenchyma, and ventricular size 1

Laboratory Investigations (Stat)

• Complete blood count to rule out anemia and infection as contributors to functional decline 1
• Basic metabolic panel including electrolytes, glucose, BUN, creatinine to identify dehydration, hyperglycemia, renal dysfunction, or electrolyte disturbances 1
• Urinalysis and urine culture to rule out urinary tract infection, which commonly causes acute urinary accidents and delirium in previously continent individuals 1
• Liver function tests given the patient's bipolar disorder and likely exposure to mood stabilizers (valproate, lithium) that require monitoring 5
• Lithium level if the patient is on lithium, as toxicity can cause confusion, tremor, and urinary symptoms 5, 6
• Valproate level if on valproate, to ensure therapeutic range and rule out toxicity 5

Additional Assessments

• Post-void residual (PVR) bladder scan to differentiate between urinary retention with overflow incontinence versus true incontinence 1, 7
• Comprehensive medication review including all prescription, over-the-counter, and psychiatric medications to assess anticholinergic burden and potential contributors to urinary retention 1, 7
• Vital signs including orthostatic blood pressure to assess for dehydration or autonomic dysfunction 1

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Immediate Management Approach

If Recurrent Subdural Hematoma is Confirmed

• Urgent neurosurgical consultation for consideration of repeat drainage, subdural-peritoneal shunt, or craniotomy depending on hematoma characteristics 3
• Post-operative subdural fluid collections with mass effect require intervention, particularly when associated with persistent psychiatric symptoms 3
• Hold antiplatelet agents and anticoagulants if present, and correct coagulopathy 2

If Normal Pressure Hydrocephalus is Suspected

• Neurosurgical evaluation for possible ventriculoperitoneal shunt placement 1
• Large-volume lumbar puncture (30-50 mL CSF removal) can be both diagnostic and temporarily therapeutic 1

If Delirium from Medical Cause

• Treat underlying infection (UTI, pneumonia, other) with appropriate antibiotics 1
• Correct metabolic abnormalities (electrolytes, glucose, renal function) 1
• Review and discontinue or reduce anticholinergic medications that may be contributing to urinary retention and confusion 1, 7

Bipolar Disorder Management During Acute Medical Illness

• Continue mood stabilizers (lithium, valproate, or atypical antipsychotics) at therapeutic doses unless contraindicated by acute medical condition 5, 6
• Avoid benzodiazepines for agitation until delirium is ruled out, as they can worsen confusion in delirious patients 2
• If severe agitation requires pharmacologic management, low-dose antipsychotic (e.g., olanzapine 2.5-5 mg, risperidone 0.5-1 mg) is preferred over benzodiazepines in the setting of possible delirium 5
• Do NOT attribute all symptoms to psychiatric illness—the new urinary incontinence and persistent irritability post-neurosurgery demand thorough medical investigation 1, 3, 4

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Critical Pitfalls to Avoid

• Never assume symptoms are purely psychiatric in a patient with recent neurosurgery and new neurological symptoms (urinary incontinence) 1, 3, 4
• Do not delay neuroimaging when recurrent subdural hematoma is suspected—chronic subdural hematoma can present with predominantly psychiatric symptoms and minimal focal neurological signs 3, 4
• Avoid attributing urinary incontinence to behavioral causes without first ruling out neurological (recurrent SDH, NPH, spinal cord pathology) and medical causes (UTI, urinary retention, metabolic derangement) 1
• Do not start or increase psychiatric medications (antidepressants, mood stabilizers, antipsychotics) until medical and neurological causes are excluded 1, 3
• Recognize that post-operative psychiatric symptoms following subdural hematoma evacuation are associated with older age, marked pre-operative psychiatric symptoms, post-operative subdural fluid collections with mass effect, and other medical comorbidities 3
• Never use antidepressant monotherapy in bipolar disorder, as it can precipitate mania, rapid cycling, and mood destabilization—always combine with a mood stabilizer 5, 6

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Expected Timeline and Follow-Up

• CT head results within 2-4 hours of presentation to emergency department 1
• Laboratory results within 2-4 hours for stat orders 1
• Neurosurgical consultation within 24 hours if imaging shows recurrent subdural hematoma or hydrocephalus 3
• Daily reassessment of mental status, urinary symptoms, and neurological examination until diagnosis is established 1
• Psychiatric follow-up once acute medical/neurological issues are addressed and stabilized 5, 6

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Long-Term Considerations After Acute Stabilization

• Patients with history of subdural hematoma who present with psychiatric symptoms and falls require high index of suspicion for recurrence 4
• Bipolar disorder patients on mood stabilizers require regular monitoring: lithium levels, renal function, thyroid function every 3-6 months 5, 6
• Fall prevention strategies and environmental modifications to reduce future head trauma risk 2
• Psychoeducation for patient and family about warning signs of recurrent subdural hematoma (worsening headache, confusion, focal weakness, seizures) 3, 4