IM Board Review

Postoperative delirium in a 64-year-old woman

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3. What clinical entity is most consistent with these physical findings, and what is the next step in management?

  • Catatonia secondary to bipolar disorder type I: challenge with intravenous lorazepam 2 mg
  • Oculomotor nerve palsy due to enlarging intracranial aneurysm: aggressive blood pressure lowering, elevation of the head of the bed
  • Toxic leukoencephalopathy: supportive care and withdrawal of the causative agent
  • NCSE: challenge with intravenous lorazepam 2 mg and order EEG

Catatonia

The DSM-5 defines catatonia as a behavioral syndrome complicating an underlying psychiatric or medical condition, as opposed to a distinct diagnosis. It is most commonly encountered in psychiatric illnesses including bipolar disorder, major depression, and schizophrenia. Akinesis, stupor, mutism, and “waxy” flexibility often dominate the clinical picture.

The pathophysiology is poorly defined, but likely involves neurotransmitter imbalances particularly with an increase in N-methyl-d-aspartate (NMDA) activity and suppression of gamma-aminobutyric acid (GABA) activity. This hypothesis is supported by the finding that benzodiazepines, electroconvulsive therapy, and NMDA antagonists such as amantadine are all effective in treating catatonia.27,28 Findings of focal neurologic abnormalities warrant further investigation. EEG may be necessary to differentiate catatonia from NCSE, as both may respond to a benzodiazepine challenge.

As pure catatonia is a diagnosis of exclusion, further workup, including EEG, is necessary to confirm the diagnosis.

Oculomotor nerve palsy

Anisocoria together with dysconjugate gaze should prompt consideration of a lesion involving the oculomotor nerve. Loss of tonic muscle activity from the lateral rectus and superior oblique cause a downward and outward gaze. Furthermore, loss of parasympathetic tone occurs with compressive palsies of the oculomotor nerve, clinically manifesting as a mydriatic and unreactive pupil with ptosis. Given its anatomic course and proximity to other vascular and parenchymal structures, the oculomotor nerve is vulnerable to compression from many sources, including aneurysmal dilation (especially of the posterior cerebral artery), uncal herniation, and inflammation of the cavernous sinus.

Noncontrast CT and lumbar puncture are very sensitive for making the diagnosis of sentinel bleeding within the first 24 hours,29 whereas computed tomographic angiography and magnetic resonance angiography can reliably detect unruptured aneurysms as small as 3 mm.30

Conditions that can lead to oculomotor palsy are unlikely to cause an acute gain in appendicular muscle tone, as noted by the catatonia this patient is demonstrating. Also, mass lesions or bleeding associated with oculomotor palsy is likely to cause acute loss of tone. Chronic upper-motor neuron lesions lead to spasticity rather than the waxy flexibility seen in this patient. In our patient, the findings of isolated anisocoria without further clinical evidence of oculomotor nerve compression make this diagnosis unlikely.

Toxic leukoencephalopathy

Toxic leukoencephalopathy—widespread destruction of myelin, particularly in the white matter tracts that support higher cortical functions—can be caused by antineoplastic agents, immunosuppressant agents, and industrial solvents, as well as by abuse of vaporized drugs such as heroin (“chasing the dragon”). In its mild forms it may cause behavioral disturbances or inattention. In severe forms, a neurobehavioral syndrome of akinetic mutism may be present and can mimic catatonia.31

The diagnosis is often based on the clinical history and neuroimaging, particularly MRI, which demonstrates hyperintensity of the white matter tracts in T2-weighted images.32

This patient does not have a clear history of exposure to an agent typically associated with toxic leukoencephalopathy and does not have the corroborating MRI findings to support this diagnosis.

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