Foot Drop in Multiple Sclerosis (MS)

Foot drop is a common and often debilitating symptom of multiple sclerosis (MS), a chronic autoimmune disease that affects the central nervous system (CNS). It results in difficulty lifting the front part of the foot, causing the foot to drag while walking. This condition can significantly impact mobility, independence, and quality of life. Understanding the connection between foot drop and MS is essential for early identification and effective management.

How MS Leads to Foot Drop?

Foot drop is not a disease in itself, but a neuromuscular symptom caused by weakness or paralysis of the muscles involved in lifting the front part of the foot, primarily the tibialis anterior. In people with MS, foot drop typically stems from damage to the nerves controlling these muscles, particularly due to lesions in the brain or spinal cord that interfere with normal signal transmission.

In multiple sclerosis, the immune system attacks the myelin sheath, the protective covering of nerve fibres in the CNS. This demyelination disrupts nerve signals between the brain and muscles. When lesions occur in areas responsible for leg movement, particularly in the motor cortex, spinal cord, or peripheral nerves, the resulting nerve damage can impair dorsiflexion (the action of lifting the foot upwards). As a result, studies estimate that approximately 40% to 50% of individuals with MS develop foot drop.

Foot drop in MS may result from:

• Central motor pathway disruption: Lesions in the upper motor neurons that control voluntary muscle movement can impair signal transmission to the lower limbs.

• Spinal cord lesions: Particularly in the cervical or thoracic spine, these can affect the pathways responsible for leg movement.

• Muscle weakness or spasticity: Common in MS, these conditions can reduce muscle control and coordination, further contributing to foot drop.

Early signs of foot drop in MS

The hallmark symptom of foot drop is difficulty lifting the front part of the foot, which can cause the toes to drag on the ground while walking. This often results in a high-stepping gait, known as a steppage gait, as the person lifts their leg higher than usual to compensate for the dragging foot.

Additional symptoms may include:

• Tripping or falling frequently

• Difficulty walking on uneven surfaces

• Pain or numbness in the foot or leg

• Fatigue due to increased effort during walking

Neurological assessment and functional evaluation of foot drop in MS

Over time, foot drop can lead to secondary problems such as muscle strain, joint pain, and postural issues, further complicating mobility.

Diagnosing foot drop in MS involves both neurological assessment and functional evaluation. A neurologist will typically:

• Review medical history, focusing on MS progression and current symptoms.

• Conduct a physical examination, testing for muscle strength, tone, and reflexes.

• Observe gait and mobility, possibly using gait analysis tools.

• Use imaging techniques, such as MRI, to identify lesions in relevant areas of the brain and spinal cord.

• Electromyography (EMG) or nerve conduction studies may be employed to assess the electrical activity in muscles and nerves.

Drop Foot in MS treatment

There is currently no cure for MS-related foot drop, but several management strategies can significantly improve function and quality of life. These include:

1. Physical Therapy

Physical therapy is a cornerstone of foot drop management. A tailored exercise program can improve muscle strength, range of motion, and coordination. Therapists may focus on strengthening the dorsiflexors and improving gait mechanics.

2. Orthotic Devices

An ankle-foot orthosis (AFO) is a common device used to stabilise the ankle and foot, preventing the foot from dragging. AFOs can be rigid or flexible, depending on the severity of the foot drop.

3. Functional Electrical Stimulation (FES)

FES is an increasingly popular treatment for MS-related foot drop. It involves applying electrical impulses to the peroneal nerve, which stimulates the dorsiflexor muscles during walking. 

4. Medications

While no medications specifically treat foot drop, some drugs can reduce related MS symptoms. For instance, baclofen or tizanidine may help manage spasticity. 

5. Surgical Intervention

In rare cases where other treatments are ineffective, surgical options such as tendon transfer surgery may be considered. This is more common in non-MS-related foot drop but may be an option in select cases.

Foot drop can have a profound impact on daily life, especially when combined with other MS symptoms like fatigue, balance issues, or cognitive changes. Support from a multidisciplinary care team — including neurologists, physiatrists, physical therapists, and occupational therapists — is crucial. Additionally, home modifications, mobility aids, and adaptive strategies can help individuals maintain independence and safety.

Foot drop in MS is a challenging symptom that can significantly limit mobility and independence. However, with proper diagnosis and a comprehensive, individualised management plan, many people can regain functional mobility and improve their quality of life.

The Health Design Collective is a group of experienced researchers who aim to advance management of foot drop in people with MS, offering hope for better outcomes and enhanced daily living for those affected.