Differential Diagnosis for the Patient's Condition
The patient's symptoms suggest a lesion affecting the brainstem, specifically the pons, which is responsible for controlling eye movements. Based on the provided information, the following differential diagnoses can be considered:
- Single most likely diagnosis
- Left paramedian pontine reticular formation (PPRF) lesion: This area is crucial for coordinating horizontal eye movements. A lesion here could explain the inability to look to the left with either eye and the failure of the left eye to move laterally when attempting to look to the right.
- Other Likely diagnoses
- Left sixth cranial nerve (abducens nerve) nucleus lesion: The sixth cranial nerve controls the lateral rectus muscle, which is responsible for abducting the eye. A lesion affecting this nucleus could result in the inability to abduct the left eye.
- Left medial longitudinal fasciculus (MLF) lesion: The MLF is a pathway that coordinates eye movements between the two sides of the brain. A lesion here could disrupt the coordination of eye movements, leading to the observed symptoms.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Brainstem stroke or hemorrhage: Although the symptoms suggest a localized lesion, it's crucial to consider the possibility of a more extensive brainstem injury, such as a stroke or hemorrhage, which could have severe and potentially life-threatening consequences.
- Multiple sclerosis: This condition can cause demyelinating lesions in the brainstem, including the pons, and could potentially lead to the observed symptoms.
- Rare diagnoses
- Tumor (e.g., glioma, metastasis) in the left pons: Although less common, a tumor in the pons could cause the observed symptoms by compressing or infiltrating the surrounding neural structures.
- Infectious or inflammatory processes (e.g., abscess, encephalitis) in the left pons: These conditions could also lead to localized damage and result in the patient's symptoms, although they are less likely than other diagnoses.