Differential Diagnosis
- Single most likely diagnosis
- Acute cerebral herniation (transtentorial herniation) due to increased intracranial pressure: This condition is suggested by the combination of a fixed and dilated pupil on one side (indicative of third cranial nerve compression) and a decreased level of consciousness. The new onset of end-stage renal disease (ESRD) could contribute to uremic encephalopathy, but the specific pupillary findings point more directly towards a structural cause like herniation.
- Other Likely diagnoses
- Uremic encephalopathy: Although the pupillary findings are not typical, uremic encephalopathy can cause altered mental status and could potentially contribute to or exacerbate other conditions leading to the observed symptoms.
- Hypertensive encephalopathy: Given the context of new ESRD, hypertension is a common comorbidity. Severe hypertension can lead to encephalopathy and, in rare cases, could cause focal neurological signs, although the specific pattern of pupillary dilation is more suggestive of a structural lesion.
- Stroke or cerebral vasculitis: These conditions could potentially cause focal neurological deficits, including pupillary abnormalities, especially if there is involvement of the brainstem or posterior circulation.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Subarachnoid hemorrhage: Although less likely given the specific pattern of symptoms, a subarachnoid hemorrhage can cause sudden altered mental status and, in some cases, pupillary abnormalities due to third nerve compression by an aneurysm.
- Meningitis or encephalitis: Infections can cause altered mental status and, in rare cases, focal neurological signs, including pupillary abnormalities. The presence of ESRD increases the risk of infections.
- Posterior reversible encephalopathy syndrome (PRES): This condition, associated with hypertension and also seen in patients with renal disease, can cause altered mental status and visual disturbances but typically presents with more symmetric neurological findings.
- Rare diagnoses
- Wernicke's encephalopathy: Although classically associated with alcoholism, Wernicke's encephalopathy can occur in malnourished patients, including those with chronic diseases like ESRD. It typically presents with ophthalmoplegia, ataxia, and altered mental status, but pupillary abnormalities can occur.
- Thrombotic thrombocytopenic purpura (TTP) or hemolytic uremic syndrome (HUS): These conditions can cause neurological symptoms due to microangiopathic changes and could potentially lead to the observed clinical presentation, although they are less likely given the specific pattern of symptoms.