The Mystery Foot continues

As at 13th September 2018. Left foot smaller and with high arch. 

Left foot - high arch 'pes cavus'

Right foot. Normal size and normal arch

Fifteen months ago, Miss T's left foot started to change. In a very short space of time, it developed a high arch (pes cavus), twisted and didn't grow as the other did. Over the weeks that followed, the changes became more pronounced. She had numerous tests and scans both at Great Ormond Street Hospital and locally (x-rays, MRIs of feet and spine, nerve conduction tests, ultrasounds, more x-rays, more MRIs etc), and met with her rheumatology team, physio and podiatrist.

Yet, all this time later, no-one could explain what was going on with her 'mystery foot'. Was it a result of her juvenile arthritis (JIA), or something else? The most recent MRI showed inflammation in the bones of her foot, but suggested this may be the result of the foot being twisted, putting mechanical stress on it, and not the cause of it.

So today we got to see another specialist - this time a paediatric foot specialist. He was very thorough, very reassuring, and went through everything. We've learnt that by keeping a record of these things right here on the blog, it can help us remember and make sense of things as time goes on so this is what we have learned as a result of today...

• Pes cavus is usually associated with a neurological cause. In around 80% of cases, the neurological cause can be found; in the remaining 20% the cause cannot be found (but may still be neurological). Working on everything he has seen, the consultant felt that at this stage a neurological issue is the most likely cause of Miss T's pes cavus.
• Although Miss T had nerve conduction tests last year, she has not yet had a full assessment by a neurologist. So she is now being referred to one.
• The original nerve conduction tests were normal, but some types of neurological issue do not give abnormal results - which is why Miss T needs to be seen by a neurology specialist.
• After the neurologist is done, we will return to this consultant to have follow-ups to see if and how the foot develops over time.

So his view is that the likely cause is neurological. Seeing a neurologist will help determine if that is the case.

If it is not, then it could be down to the JIA although he said he hasn't come across this scenario of JIA causing pes cavus before. When Miss T first developed JIA, it was her left foot that was most badly affected and it took a while to get the inflammation under control. In theory, it is possible that the JIA damaged the growth plates in her left foot, which is why it is not growing properly now leading to a smaller foot and the pes cavus. 

We were previously advised that progressive casting (where the foot is stretched and set in a cast, then repeated) was an option. Today we heard that progressive casting does not usually work for a pes cavus. So, depending on how it develops and any symptoms Miss T develops (such as pain when walking), the only option to 'fix' it would be surgery. That sounds scary, but we were reassured that she doesn't need surgery at the moment.

Miss T's foot was also described again as a mystery.

So, next steps for Miss T:

• Referral to a neurologist.
• Return to this consultant to monitor over time.
• If it gets worse and causes problems, consider surgery.