Teaching Case

A 50-year-old left-hand dominant male patient came to our hospital. He presented a painful and cold sensation in the left palm. The patient was a mechanic by profession.

An ultrasound study was performed showing an anechoic formation of 18.8 mm x 13.2 mm by 12.8 mm in the hypothenar eminence with an echogenic content close to the wall in relation to mural thrombus. The neck of the lesion measures 1.3 mm. (Fig. 1)
With colour Doppler US, flow movement is observed inside (yin-yang sign). It is suggestive of corresponding with an aneurysm of the cubital artery. (Fig. 2)
The CT angiography showed a contained vascular injury dependent on the ulnar artery with maximum diameters of 19 x 16 mm and a true light of 13 x 12 mm. The lesion had a saccular form with an irregular wall and was partially thrombosed. The afferent artery measured 2.5 mm and the efferent artery 3 mm. (Fig. 3, 4)

- The hypothenar hammer syndrome (HHS) occurs from a repetitive trauma to the distal ulnar artery and superficial palm arch to the hypothenar eminence (hook of hamate). This continued trauma causes damage of the arterial intima, which can lead to aneurysm formation with or without vessel thrombus and promotes the microemboli generation. HHS is usually caused by microtrauma, but it may also present acutely following a single severe blow to the hypothenar eminence. [1, 2]
The difference between an aneurysm and pseudoaneurysm is based on histology. Aneurysm is a dilatation of the artery and is composed of the normal histological components, while pseudo-aneurysm is a walled-off collection of blood outside a damaged artery that does not contain the normal histological components.
- The usual clinical presentation is a cold and painful feeling in the palm and ischaemia of the fourth and fifth fingers because of the microemboli.

- The diagnosis can be confirmed easily with US but conventional angiography, CT angiography, or MR angiography can be useful in order to choose the most appropriate treatment. [3-5]

- There are several strategies for treatment of HHS. The non-surgical treatment included: smoking cessation, cold avoidance, calcium channel blockers, antiplatelet agents or anticoagulation and pentoxifylline to reduce blood viscosity.
Surgical options include arterial ligation, resection of thrombosed arterial segment or aneurysm with end-to-end anastomosis, resection and vascular reconstruction with vein or artery graft. [5, 6] This patient was managed by resection of thrombosed aneurysm with end-to-end anastomosis.

- In conclusion, hypothenar hammer syndrome may not be so rare nowadays. Physicians and radiologists should be familiar with this aetiology because it is a reversible and preventable cause of upper extremity digital ischaemia.