Finger ganglion (Digital Myxoid Pseudocyst, Mucous Cyst) is a fluid-filled sac that forms on the finger, typically between the last joint and the fingernail, but can reside anywhere along the finger too. Cysts found in proximity of the nail, very often sit on the top of nail root (known as germinal matrix) causing characteristic nail grooving (Picture 1, Gallery below). Vast majority of these lesions are connected to the nearby finger joint by a stalk and arise as a consequence of an underlying joint lining tear, degeneration and/or osteoarthritis (Picture 2, Gallery below). Even successful removal of mucous cyst may therefore, not abolish pain entirely, but it usually alleviates it markedly especially if painful, arthritic bony spurs of the joint are cleared at the same time.

Why exactly these lesions develop remains unknown, but clinical observations always suggest pathology of the underlying finger joint. Abnormality of the joint lining and capsule caused by either trauma or chronic degenerative changes (arthritis) are most commonly seen.

One theory suggests that mucous cysts are formed when connective tissue degenerates (wears away). The leftover collagen is thought to collect in pools, and the pools form cysts. Fluid in the cyst sac (the same one that lubritates the joint) seems to move in one direction only – from the joint into the cyst, but not the other way hence its gradual, slow increase in size, especially if left untreated.

A mucous cyst is typically superficial, visible just under the skin that surrounds the nail. Thinning of the overlying skin which becomes almost a ‘see through’ thin (Picture 1, Gallery below) is very common. As the ganglion continues to grow and becomes more prominent, it frequently gets caught which can elicits a lot discomfort and most commonly prompts patient to seek removal. It may be painful, but underlying arthritis more than the ganglion itself, usually causes this pain. Patients should therefore, not be surprised if even after successful ganglion removal some discomfort remains. A groove in the nail is very emblematic and results from nail root (germinal matrix) compression by the cyst.

Diagnosis usually very straightforward and unambiguous. If significant arthritis is suspected, X-rays might be required to ascertain degeneration related to osteoarthritis – joint space narrowing and/or bone spurs and irregularities which might need addressing at the time of cyst removal.

Mucous cysts often do not need to be treated – observation is sufficient for majority of lesions. Spontaneous disappearance is however, only seen in very small, tiny ganglions, not long standing, larger ones.

Surgery should be reserved for symptomatic lesions – steady enlargement, infections, recurring discharges, pain, repeat traumas etc.

Sometimes a mucous cyst ruptures spontaneously. Rupture creates a path into the joint where bacteria could enter and cause a serious infection inside the joint. When this happens, antibiotics are applied over the ganglion, finger is wrapped in a dressing and oral antibiotics are prescribed. If the joint develops an infection despite these steps, surgery is required. Repeated ruptures are best treated surgically in order to reduce the risk of infections and further inconveniences.

Needle puncture is one option (although not my favourite). It allows partial drainage of the gelatinous filling and deflation of the cyst. Aspiration is rarely possible as ganglion filling is very viscous and usually too thick even for large needles. Aspiration usually has less than a 50 % success rate as it does not remove the sac nor it addresses underlying arthritis which causes ganglion in the first place.

Personally, I am usually reluctant to offer patients needle punctures as those do not address the problem,  yet expose patients to unpleasant intervention and conversion of “closed” abnormality into “open” one, exposed to infection. If and when anything needs to be done, then radical, yet meticulous surgical removal of the cyst at least, offers a chance of eradicating problem permanently.

The most permanent solution is surgical removal (excision) of the cyst and its connection to the joint. This procedure also allows cleaning/washout (debridement) of the arthritic joint and its bony spurs which leads to significant pain relief. If the skin on the finger is too closely attached to the cyst, and/or becomes very thinned by ganglion enlargement, it should be removed together with the ganglion. Defect can then be covered with a small skin graft or more frequently, local flap (Pictures 3-6, Gallery below). All of this surgery can comfortably be done under local anaesthetic whereby only the finger is numbed.

After operation only finger is covered with dressings (Picture 7, Gallery below) and patient advised to keep the finger dry for 10-12 days. In most cases it is mobilised with the dressings in place, straight after surgery. If more extensive work is carried out to the joint itself or large flap/graft was required, splint can be applied across the joint for 1-2 weeks. You will be advised how to exercises the finger in order to regain full motion quickly. Exercises should be continued until you can move the finger normally without pain.

Healthy, new, non-grooved nail growing (Picture 8, Gallery below) several weeks after the surgery is a testimony of adequate removal. Such successful outcome is however not visible in less then 6-8 weeks from surgery.

Complications are rare, but as with any surgical procedure, there are general and mucous cyst-specific risks which patients should be aware of:

General complications:

• Skin/wound infection
• Scarring – the scar will take up to a year to mature. Scar massage after your surgery will help to reduce discomfort. In some cases the scar can become thickened, red and painful, known as either a keloid or hypertrophic scar.
• Hypertrophic (lumpy and itchy) scarring
• Stiffness – if operated finger is not mobilised very early
• Complex Regional Pain Syndrome (CRPS) – rarely people are sensitive to hand surgery and their (seen in 5% of surgery) hand may become very swollen, painful and stiff after any operation. This problem cannot be predicted but will be watched for afterwards and can be treated with medication and hand therapy

Procedure specific risks:

• scar sensitivity
• cyst recurrence
• persistant nail irregularity