Also known as: CIPA
Hannah's pre-existing CIPA condition is central to the episode's diagnostic challenge, as her inability to feel pain makes it extremely difficult to localize the source of her acute illness and leads to multiple complications.
The underlying cause of Hannah's acute symptoms is B12 deficiency caused by a tapeworm infection. This drives the main diagnostic mystery of the episode, manifesting in progressive neurological deterioration, psychiatric symptoms, and paralysis.
Also known as: Tapeworm infection
The tapeworm (acquired from undercooked fish) is consuming Hannah's B12, causing all her acute symptoms. House dramatically removes a 25-foot tapeworm from her abdomen in the resolution of the case.
Also known as: Nerve damage, numbness
The nerve biopsy reveals severe demyelination (loss of nerve insulation) progressing from outside in, indicating a systemic cause rather than primary nerve disease. This is a key finding that points toward the B12 deficiency diagnosis.
Also known as: Head trauma
Hannah's mother sustains severe head trauma in the car accident and requires emergency surgery with complications (brain swelling) necessitating a second operation. Her condition drives Hannah's emotional state throughout the episode.