MKSAP Quiz: 2-month history of foot pain
A 42-year-old woman is evaluated for a 2-month history of left foot pain between the third and fourth toes, accompanied by a burning sensation and the sensation of walking on a pebble. She has not experienced any trauma in the area, and she does not have edema or erythema. Following a physical exam, what is the most likely diagnosis?
A 42-year-old woman is evaluated for a 2-month history of left foot pain between the third and fourth toes, accompanied by a burning sensation and the sensation of walking on a pebble. She has not experienced any trauma in the area, and she does not have edema or erythema. Symptom onset was insidious, and the pain only occurs when she is standing or walking. She works as a restaurant hostess and wears high-heeled shoes for her job.
On physical examination, vital signs are normal. The left foot appears normal, with no palpable abnormalities or tenderness between the third and fourth toes. Sensation is intact throughout the foot, and posterior tibial and dorsalis pedis pulses are palpable.
Which of the following is the most likely diagnosis?
A. Bunion deformity
B. Hammertoe deformity
C. Morton neuroma
D. Plantar fasciitis
MKSAP Answer and Critique
The correct answer is C. Morton neuroma. This content is available to MKSAP 18 subscribers as Question 136 in the General Internal Medicine section. More information about MKSAP is available online.
This patient's symptoms are most likely due to a Morton neuroma, a condition that causes compression of the interdigital nerve. Common symptoms include paresthesias and the sensation of walking on a pebble. On examination, there are usually no obvious abnormalities, but some patients may have tenderness to direct palpation of the involved interspace. The cause is thought to be use of constricting footwear, such as high-heeled shoes. First-line therapy consists of wearing nonconstricting footwear and local padding. In patients who do not respond to these measures, a local glucocorticoid injection can be offered. For recalcitrant cases, sclerosing alcohol injections, radiofrequency ablation, and surgery (neurectomy) have been used with some success.
Bunion (hallux) deformity refers to lateral deviation of the great toe with medial bone deformity. This condition typically causes pain at the site of the deformity due to footwear pressure. The location of this patient's pain and lack of visible deformity on examination make bunion deformity an incorrect diagnosis.
Hammertoe deformity is also associated with constricting footwear; it refers to a proximal interphalangeal joint flexion deformity with dorsal interphalangeal joint extension and extended or neutral position of the metatarsophalangeal joint. This patient's normal foot appearance makes this diagnosis incorrect.
Plantar fasciitis typically causes pain localized to the medial inferior heel at the insertion of the plantar fascia in the medial calcaneal tubercle. Pain is usually present at activity initiation following prolonged rest and improves with further walking (for example, the first few steps in the morning after arising from bed). As the condition progresses, pain may be present with both activity and rest. The location and description of this patient's pain are not consistent with plantar fasciitis.
Key Point
- Hallmarks of a Morton neuroma are pain between the metatarsal heads, the sensation of walking on a pebble, and no obvious abnormalities of the foot upon clinical examination or palpation.