A couple of questions about foot drop and their answers

 

 

Two of the readers of my blog asked me about foot drop. Their questions are given below. My response to them follows.

QUESTION

lu Hi there,
Really need some advice/information. About 5-6 weeks ago i started noticing that my left foot felt funny, tingling and numb, and i was also experiencing some problems walking but i couldn’t quite pinpoint it and thought it would go away. I started to realise that i couldn’t dorsiflex my left foot, it felt numb and tingly on the top of my foot and to half way up the shin. After spending a few days trying to exercise my foot i regained some minimal dorsiflexion (about half capacity compared to my normal right leg) I have no pain and minimal discomfort (the bones on the top of my foot and around my ankle are starting to ache as i constantly try and flex my muscles/toes to improve action). I have been told by my GP that i have drop foot, which i’d already suspected, but i can’t get an appointment for another 7 weeks with an orthapaedic consultant and i am starting to really stress myself out reading so much on the internet that it might be ALS/MS or some serious underlying condition. I’m mid-twenties, female and was totally free of health issues until this incident. I don’t know whether I should push my doctor for an earlier referral – i have no other symptoms and can get about but walking is becoming tiring and upsetting. The condition has not deteriorated but nor has it improved much – I was praying that it was simply a transient problem but after 6 weeks i’m not so sure. I haven’t suffered any discernible trauma or injury (except i remember carrying a heavy bag and wearing heels for a few hours which made my foot hurt prior to these symptoms). Please if you can offer any info/assurances that it is common to have something like this out of the blue, it would be much appreciated.

 

Dear Lu,
thank you for writing in to me. You say you are in your mid-twenties so first let me reassure you. More than likely you do not have anything serious such as amyotrophic lateral sclerosis (ALS) or multiple sclerosis (MS). Let us first discuss ALS since that is a scary disease indeed. ALS does at times start off with an innocuous foot drop but you are not in the right age group for it. Usually ALS is a disease which strikes people in their fifth or sixth decade of life. Familial ALS begins at a younger age but here the history is of multiple family members having ALS at a young age.

Now let us come to MS. MS can have myriad clinical presentations. While it can present with foot drop it is usually not a common presentation. More common presentation of MS in a young lady like you is an attack of optic neuritis (sudden loss/blurring of vision in one eye along with pain) or an incomplete transverse myelitis (TM). Patients with TM depending upon the level of involvement of the spinal cord (usually it is in the cervical cord) may present with weakness in the legs, numbness, loss of bladder control, problems with gait and balance.

So most likely you have a foot drop due to either peroneal nerve palsy or sciatic nerve palsy. Now you deny any trauma. At times the cause of peroneal nerve palsy can be “subtle” such as repeated crossing and uncrossing of the legs (in thin persons), falling asleep with the outer aspect of the knee (near the head of the fibula) pressing against something hard such as a bed railing and so forth or something pressing on the sciatic nerve (as it exits the pelvis) or at the level of the fibular head (peroneal nerve) . Rapid changes in body weight may make a person predisposed to compression palsies of various peripheral nerves. This is especially common in people who have marginal diets, alcoholic and diabetics.

My advice to you though would be to follow up with you GP. He/ she shall be the best person to guide the workup forward. I hope I have been able to offer you some useful advice.

Personal Regards,

Nitin Sethi, MD

QUESTION

Dear Dr Sethi,

Two months ago I had THR with a spinal block. Upon the spinal wearing off my right foot and leg from the knee down remained numb and I was left with foot drop.

Physical Therapy and a NEMS stimulator are not helping. The pins and needles feeling is lessening but still have tingling in my toes, top of my foot in certain positions. I have to constantly wear an AFO to walk or drive but it is very uncomfortable. The Surgeon thought my foot would come back by now but no improvement. If anything it seems worse.

What could have caused this? I was fine prior to the surgery. Is there any hope of my foot coming back? What can I do? I do not wear a brace at night and have tried Nuerontin to no avail.

Thank you, Lynee

Dear Lynne,
thank you for writing in. Foot drop can occur as a complication of total hip replacement surgery. The cause of the foot drop is usually pressure/ stretching of the fibers of the sciatic nerve. This can occur during the surgery itself or may occur due to the way the hip/limb was positioned during the surgical procedure. If the injury is a simple neurapraxia (pressure on the nerve), the nerve usually recovers fully in due course of time. Since two months have passed since your total hip replacement surgery and your foot drop persists it would be advisable that a nerve conduction study (NCV) be carried out. A good nerve conduction and electomyography (EMG) study shall give useful prognostic information namely to what extent is the nerve damaged and is the nerve regenerating? Also nowdays a high quality MRI scan can actually image the sciatic nerve itself.
The best person to guide you forward shall be your orthopedic surgeon and primary care physician. I wish you my very best.

Personal Regards,

Nitin Sethi, MD

Foot drop: making sense of its causes

A common problem for which patients consult neurologists like me is foot drop. As the name says, they have foot drop and hence are unable to dorsiflex their foot. As a result they are likely to catch their foot on the ground while walking and thus are prone to falls and this brings them to medical attention. Foot drop should be differentiated from frail foot. In foot drop, patients are unable to dorsiflex their foot while those who have a frail foot are unable to dorsiflex as well as unable to planter flex the foot (that is they are unable to pull their foot up or push down their foot as when you press down on a gas pedal).

Foot drop might occur suddenly (acutely) or may be more insidious and the causes for both vary. Before we discuss the causes of foot drop, it is helpful to know a little about the relevant anatomy. The muscle which helps to dorsiflex the foot is called tibialis anterior and it is supplied by a nerve called the peroneal nerve. The peroneal nerve is a branch of the sciatic nerve. The sciatic nerve is formed by the lower lumbar and sacral nerve roots and forms a part of the lumbosacral plexus. The peroneal nerve in the knee area is quite superficial as it cross the neck of the fibula (fibula is one of the bones in the lower leg along with the larger tibia). As the nerve is superficial it is prone to compression across the neck of the fibula.

So lets now discuss some of the common causes of foot drop. If suppose you suffer a fracture across the neck of the fibula, or have a gun shot wound to that area, or during knee surgery the peroneal nerve is accidently transected, you shall develop a foot drop. In all of the above the cause is injury to the peroneal nerve.

But peroneal compression may also occur due to other more subtle causes. One of the most common causes of foot drop is habitual leg crossing. This is most commonly seen in obese persons or in diabetics who lose weight.  After weight loss they can cross their legs more easily and may develop a foot drop. Why does this occur you may ask? Well the answer is simple, as I told you before the peroneal nerve is quite superficial and hence prone to compression. When you cross your leg, the nerve may get pinched against the other knee and if you do not relieve the pressure soon, you can develop a foot drop. A common scenario is that the person is sitting with his legs crossed on a long flight, or might have fallen asleep with his leg pressed against the side rails of the bed (this is common in hospitalized patients in the intensive care unit or also when patients are undergoing surgery in the OR), they wake up and find they have a foot drop. The good news is that the prognosis for this type of compression injury to the peroneal nerve is rather good. Once the pressure is released, these patients usually make a full recovery over a few days to weeks and their foot drop goes away.

They can though be other more proximal causes of foot drop. You can have compression or injury to the sciatic nerve or to the lumbosacral plexus (remember I told you, that the peroneal nerve is a branch of the sciatic nerve).  Compression of the sciatic nerve may at times be due to a tumor or mass in the pelvis or in the thigh or knee area.

Lower lumbar disc herniation may also result in a drop foot. This is commonly seen in L5 disc herniation. Patients usually present with radicular pain radiating down the leg, though sometimes this may be absent.

Diagnosis and management of foot drop: the diagnosis of foot drop is clinical and depending upon your examination findings, your doctor may or may not order other tests to confirm at what level is the problem. He may order a nerve conduction study and an EMG (needle study, electromyogram) to check for the the sciatic and peroneal nerves. If warranted an MRI of the lower back and of the plexus may be done.

The treatment depends upon the cause. If the foot drop is because of habitual leg crossing, then all what may be needed is to advise the patient not to cross his legs. The recovery is spontaneous. If a mass is the cause then well depending upon what it is, the treatment varies. Patients usually need a ankle foot orthosis or a foot drop splint. This splints the foot up and prevents fall.

I hope this is helpful to some of you.

Personal Regards,

Nitin Sethi, MD