Common Foot Neurological Conditions

Paul Strobel DPM ***

No relevant financial or nonfinancial relationships exist. Nerve related foot conditions

 Morton’s neuroma  Pes Cavus (high arch foot)  Tarsal Tunnel Syndrome  Foot Drop  Diabetic Peripheral Neuropathy  Charcot foot Morton’s Neuroma

 An entrapment of the plantar intermetatarsal nerve, most commonly between the 3,4 metatarsals, but may involve any intermetatarsal space.  Typically more painful with shoes as there is increased pressure on the nerve.  Patients complain of burning pain that often radiates to the toes, may describe a “rolled up sock” sensation in the forefoot.

Morton’s Neuroma: exam

 Mulder’s sign: Pain on palpation of the involved interspace with or without side‐to‐side pressure applied to the metatarsal heads.  MRI: may show if enlarged moderate/significantly.  Diagnostic injection. Morton’s Neuroma: treatment

 Adequate fitting shoes  Metatarsal/neuroma pads  NSAID’s  Corticosteroid injections  Nerve alcohol sclerosing injections  Surgery to decompress or resect the nerve  Physical Therapy Morton’s Neuroma Pes Cavus (High Arch) Foot

 Cavus foot can be linked to central and peripheral neurological diseases.  Ex: polio, Charcot‐Marie‐Tooth disease, Friedreich’s ataxia, cerebral palsy.  Up to 2/3 of patients with symptomatic cavus have an underlying neurological disorder. The most common is CMT.  Electromyography, NCV, sural nerve biopsy testing can help diagnose underlying causes. Pes Cavus (High Arch) Foot

 Subtle cavus can be non‐ neurological and is likely genetic.  Often biomechanically induced with plantarflexed first ray and hyperactive peroneus longus muscle. Pes Cavus (High Arch) Foot

 Difficult to manage due to rigid nature of the foot.  Patient’s typically overload the lateral column of the foot.  Common symptoms: ankle instability, peroneal tendonitis, lateral tibial stress syndrome, iliotibial band syndrome. Cavus foot: treatment

 Orthotics: to help distribute pressures more evenly across the foot.  Foot and ankle bracing for neurological conditions.  Physical therapy to help reduce muscle imbalances.  Surgical intervention for instability, weakness, pain.

Tarsal Tunnel Syndrome

 Entrapment of the posterior tibial nerve or a branch in the tarsal canal by the flexor retinaculum, fibro‐osseous tunnels, or the deep fascia. Tarsal Tunnel Syndrome: etiologies

 Tumor, cyst in the tarsal canal  Fracture fragment of calcaneus pressing on the nerve  Severe flatfoot causing stretching of the nerve.  Enlarged blood vessels/varicose veins  Generalized leg edema  Metabolic causes: Diabetes Tarsal Tunnel: diagnosis

 Burning, stabbing, tingling at the bottom of the foot and inside of the ankle.  Pain to the tarsal tunnel increase with activity and relieved by rest.  Sensory loss in the plantar foot, medial ankle.  Positive Tinel’s sign at tarsal tunnel.  X‐ray for bony pathology, MRI for soft tissue pathology.  Nerve conduction studies. Tarsal Tunnel: conservative treatment

 NSAID’s  Localized steroid injection.  Immobilization.  Orthotics to control foot function.  Physical therapy: iontophoresis.  Gabepentin, Lyrica, Voltaren gel. Tarsal Tunnel: surgical treatment

 Removal of cyst, tumor, varicose vein in canal.  Decompression of the tarsal tunnel. (Similar idea as carpal tunnel release) Foot Drop

 Weakness of ankle dorsiflexion from deep peroneal nerve compromise.  Physical findings may include: difficulty clearing the foot during swing phase of gait (toes dragging or catching on the floor), foot slap, paresthesia's with distribution of common peroneal nerve.

Foot Drop: etiologies

1. Radiculopathy L4/L5 –disc herniation or foraminal stenosis. 2. Common peroneal neuropathy: ‐external compression; bed rails, below knee cast, trauma ‐rapid weight loss ‐traction during knee surgery, ‐ ‐inversion/plantarflexion ankle injury 3. UMN causes: CVA, ALS, MS, brain tumor, spinal cord injury. 4. Micronutrient deficiency: (Vitamin B 12 post bariatric surgery) Foot Drop: diagnosis

 Neurological exam: motor strength testing, reflexes.  Nerve conduction, EMG testing.  Lab studies for metabolic or toxic causes if no trauma or obvious cause. BS, Hemoglobin A1c, ESR, CRP, BUN, Vit. B12, creatinine.  Imaging: x‐rays to evaluate for fracture tibia/fibula, MRI to evaluate for bone injury, brain/spine injury, nerve root impingement. Foot Drop: treatment

 Bracing with AFO (Ankle Foot Orthotic), help dorsiflexion during swing phase of gait and provide stability.  Medications: antidepressants (amitriptyline, gabapentin, lyrica), oral and topical NSAID’s  Nerve blocks.  Functional Electrical Stimulation: may help if bracing does not fit or work. Foot Drop: treatment

 Team approach is useful: physical medicine rehabilitation, podiatry, interventional spine, orthotist/prosthetist, physical therapist.  Surgery: (if conservative treatment fails)  Decompression of fibular nerve, sciatic nerve, nerve root, spinal cord, brain tumor.  Foot and ankle arthrodesis near ankle joint, tendon transfers.  Repair of nerve or tendon injury if traumatic cause. Diabetic Peripheral Neuropathy

 Most common form of neuropathy in the developed world.  Found in about 25% of diabetics.  Distal symmetric polyneuropathy –stocking‐ glove pattern in hands and feet.  Factors involved: poor glycemic control, duration of diabetes, hyperlipidemia, elevated albumin, obesity. Diabetic Peripheral Neuropathy: treatment

 Medications: Lyrica, cymbalta, gabapentin, amitriptyline.  Topicals: lidocaine patches, capsaicin cream.  TENs unit.  Treatment can help reduce symptoms and progression. Diabetic Peripheral Neuropathy

• Patient role:  Control diabetes and blood sugars.  Adequate nutrition.  Control Vitamin deficiency: Vit. B1,B6,B12  Maintain a healthy weight. Diabetic Peripheral Neuropathy

 Patient’s at risk of foot and ankle ulceration because they cannot feel pain or sore areas.  Runners and walkers need to have cushioned well fitting shoes.  Encourage daily foot checks for problems.  Be seen urgently if any problems are noted to help reduce chance of infection or amputation. Charcot Foot

 Charcot neuroarthropathy: unilateral redness and swelling of a lower extremity.  Foot/ankle bones begin to soften, fracture, displace. “bag of bones”  Due to coexisting peripheral neuropathy most patient’s do not have pain.  Can occur with other peripheral neurology etiologies: ex: alcoholic or metabolic. Charcot Foot

 0.1‐5% of patients with peripheral neuropathy will develop Charcot arthopathy.  Onset usually after average of 15 years of Diabetes Mellitus history.  50‐60 years of age

Charcot foot: etiology

 2 main theories: (likely a combination)  Neurovascular: vascular damage to autonomic nervous system causes reflex hyperemia and increase in blood flow to the limbs. (Washes out the bones)  Neurotraumatic: microtrauma initiates an inflammatory cascade leading to breakdown. Charcot foot: diagnosis

 Physical exam: warm, red, swollen foot. Increased temperature from contralateral foot.  Imaging: Bone scan, MRI, X‐ray.  In presence of open wounds, infection can be very difficult to differentiate.  May need bone biopsy, cultures.  Be cautious in diabetic neuropathic patient having unilateral foot and ankle swelling and/or fractures without history of trauma. Charcot foot: treatment

 Medications: biguanides and bisphosphonates, intranasal calcitonin.  Immobilization foot and ankle: CAM boot,  Total contact or below knee cast with non weight bearing.  Bones can take 3‐6 months to begin to stabilize and a full year to heal.  Once temperature reduces and bones begin to stabilize then CROW boot and long term a diabetic shoe.

Charcot foot: treatment

 If foot and ankle become a rocker bottom type foot or are unstable then surgical intervention may be needed.  Surgical arthrodesis of foot and ankle.  Removal of bone spur.  Significant risk of ulcerations, infections leading to amputation. Charcot Foot reconstruction References

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 Results of surgical treatment of tarsal tunnel syndrome.  Reichert P, Zimmer K, Wnukiewicz W, Kuliński S, Mazurek P, Gosk J.  Foot Ankle Surg. 2015 Mar;21(1):26‐9. doi: 10.1016/j.fas.2014.08.013.  PMID:25682403  Entrapment neuropathy about the foot and ankle: an update.  Pomeroy G, Wilton J, Anthony S.  J Am Acad Orthop Surg. 2015 Jan;23(1):58‐66. doi: 10.5435/JAAOS‐23‐01‐58. Review.  PMID:25538131  Decompressive Surgery for Diabetic Neuropathy: Waiting for Incontrovertible Proof.  Tannemaat MR, Datema M, van Dijk JG, Midha R, Malessy MJ.  Neurosurgery. 2016 Dec;79(6):783‐785.  PMID:27861415  The Charcot foot: pathophysiology, diagnosis and classification.  Trieb K.  Bone Joint J. 2016 Sep;98‐B(9):1155‐9. doi: 10.1302/0301‐620X.98B9.37038. Review.  PMID:27587513  Treating Painful Diabetic Peripheral Neuropathy: An Update.  Snyder MJ, Gibbs LM, Lindsay TJ.  Am Fam Physician. 2016 Aug 1;94(3):227‐34.  PMID:27479625  Peroneal nerve palsy after compression stockings application.  Kim JH, Kim WI, Kim JY, Choe WJ.  Saudi J Anaesth. 2016 Oct‐Dec;10(4):462‐464.  PMID:27833497 References cont.

 Foot Drop: Looking Beyond Common Peroneal Nerve Palsy: A Neurophysiology Centre Experience.  Yap SM, McNamara B.  Ir Med J. 2016 Apr 11;109(4):388.  PMID:27685482

 A prospective study of midfoot osteotomy combined with adjacent joint sparing internal fixation in treatment of rigid pes cavus deformity (PDF Download Available). Available from: https://www.researchgate.net/publication/262884005_A_prospective_study_of_midfoot_osteotomy_combined_with_adjacent_joint_sparing_i nternal_fixation_in_treatment_of_rigid_pes_cavus_deformity [accessed Jan 4, 2017]

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