Which nerve causes a burning sensation to the distal and medial hallux?

The Medial Dorsal Cutaneous Nerve Causes Burning Sensation to the Distal and Medial Hallux

The burning sensation to the distal and medial hallux is most commonly caused by the medial dorsal cutaneous nerve, which is a terminal branch of the superficial peroneal nerve. 1, 2

Neuroanatomy of the Hallux

• The medial dorsal cutaneous nerve (MDCN) is a terminal branch of the superficial peroneal nerve that provides sensory innervation to the dorsomedial aspect of the hallux (big toe) 1
• The MDCN typically courses 2.9 mm lateral to the first tarsometatarsal joint, passes deep to the extensor hallucis brevis tendon, and bifurcates in the midmetatarsal region 1
• The nerve then arborizes to supply sensibility to the first toe interspace and the adjacent sides of the first and second toes, including the distal and medial hallux 1, 2

Clinical Significance

• Burning sensations in the distal and medial hallux often represent neuropathic pain, which may manifest as dysesthesias (unpleasant abnormal sensations of burning and tingling) 3
• The distance between the dorsomedial cutaneous nerve to hallux and the extensor hallucis longus tendon varies based on hallux valgus severity, ranging from 12 mm in normal feet to 19 mm in severely deformed feet 2
• This anatomical relationship creates a "danger zone" during surgical approaches to the first metatarsophalangeal joint, where nerve damage can lead to debilitating symptoms 2

Differential Diagnosis

• Deep peroneal nerve involvement can also cause symptoms in the first dorsal web space but typically presents with pain radiating to this area rather than isolated burning of the medial hallux 4
• Small fiber neuropathy can affect the hallux and present with burning pain, dysesthesias, and numbness 5
• Distal sensory polyneuropathy often begins in the toes and can cause burning sensations, particularly in patients with diabetes 3
• Entrapment neuropathies of the foot may mimic these symptoms but usually have a more specific distribution corresponding to the entrapped nerve 4

Diagnostic Approach

• Clinical assessment should include testing of small-fiber function (pinprick and temperature sensation) and large-fiber function (vibration sensation using a 128-Hz tuning fork) 3, 5
• Protective sensation should be assessed using a 10-g monofilament test, particularly in patients with diabetes 3
• Electrodiagnostic studies can help confirm the diagnosis, with nerve conduction studies showing slower conduction velocity in the distal superficial peroneal nerve compared to its proximal portion (by 8-14 m/s) 6
• MRI of the lumbosacral plexus may be appropriate in cases where the etiology remains unclear after clinical and electrodiagnostic evaluation 3

Management Considerations

• Treatment should address the underlying cause of the neuropathic pain
• Neuropathic pain medications may be indicated for symptomatic relief 3
• Surgical approaches to the first metatarsophalangeal joint should avoid the identified "danger zone" (12-19 mm medial from the extensor hallucis longus tendon) to prevent iatrogenic nerve injury 2
• A mid-medial surgical approach to the metatarsophalangeal joint is preferred as it falls outside this danger zone 2

Understanding the specific nerve anatomy is crucial for both diagnosis and treatment planning, particularly when considering surgical interventions that might place this nerve at risk.