What is occult spinal dysraphism?

Spinal dysraphism is a term used to describe a broad spectrum of abnormalities resulting from the improper formation of a baby’s spine and spinal cord in the very early stages of pregnancy.¹ The most common form of spinal dysraphism is spina bifida, in which a gap in the spine is present.^2,3 Spinal dysraphism can be ‘open’, meaning the spinal cord or spinal fluid protrudes outside the body into a sac, or ‘closed’, when the malformed area is covered by skin.^3,4 

Occult spinal dysraphism (OSD) encompasses the closed spinal anomalies (‘occult’ means ‘hidden’). In many cases, a small skin marker is present, namely a dimple, a birthmark or a hairy patch. Due to the hidden nature of these conditions, most people with this type may be unaware of its presence.⁴ The most common form of closed spinal dysraphism is a spinal lipoma, a fatty lesion attached to the spinal cord.⁴ Some more examples of closed spinal abnormalities include:¹

• Diastematomyelia (a split in the spinal cord)
• Tight Filum Terminale (abnormal tension on the lower part of the spinal cord)
• Dorsal Dermal Sinus (a deep dimple or hole which can cause infections)
• Spina Bifida Occulta (malformation of the vertebrae, without involvement of the spinal cord)

Symptoms and complications

Sometimes, an abnormality of the skin present from birth can be a visible sign of a spinal malformation. The following are important markers that warrant further investigation, particularly if two or more signs are present.⁵ They are most commonly located on the lower back. Studies have found lipomas (fatty lumps) to be the most common skin marker associated with OSD. Other visible signs that could indicate a problem include:

• Patch of hair
• Abnormal dimple on the lower back
• Skin tag that looks like a miniature tail
• Red or purple spots
• Hyperpigmentation

Unfortunately, skin markers are not always present at birth in cases of occult spinal dysraphism. Therefore, a diagnosis may be made later in life when symptoms of nerve damage become apparent.^4,5 

While many cases of occult spinal dysraphism are mild and do not require treatment, complications can arise, which affect the individual’s quality of life. The following symptoms can be signs of serious complications:⁴

• Bladder and bowel issues such as increased urgency to urinate, incontinence, and constipation
• Foot deformities
• Scoliosis (a curvature in the spine)
• Lower back and leg pain
• Lower limb weakness
• Changes in sensation in the feet and/or legs, such as numbness or tingling
• Clumsiness
• Difficulty with walking
• Meningitis caused by recurrent infections
• Recurring urinary tract infection

If a person with an OSD develops any of these symptoms, a condition called tethered cord syndrome is usually suspected. This means that the spinal cord is constantly being pulled on because it is abnormally attached to the spinal canal, instead of being able to move freely. This creates friction and damages the nerves. Symptoms of tethered cord syndrome can present at birth or during childhood, usually between the ages 5-15 years old. Rarely, they can also present for the first time during adulthood. Symptoms can worsen progressively over time if the tethered cord is left untreated, but if diagnosed and treated early, the damage can be reversible.⁴

Diagnosis of occult spinal dysraphism

Unlike open spinal dysraphisms, which are identified during pregnancy by ultrasound and MRI scans, occult dysraphism can go undiagnosed until skin anomalies prompt further investigation, spinal deformities are discovered incidentally on an MRI scan, or the patient starts experiencing symptoms. Early diagnosis is ideal in order to prevent worsening nerve damage caused by complications. However, this can be difficult as the spinal abnormalities are usually hidden. There are also no valid genetic screening tests available to predict them. Any skin anomalies that could be related to OSD should be investigated.⁴

After considering skin markers and/or symptoms, medical scans are essential for diagnosis. Usually, babies under 3 months old will have an ultrasound of the back for older babies, children and adults, an MRI scan is used.^4,6 

Treatment and management

Treatment of OSD depends on the underlying spinal malformation and the severity of the symptoms. However, surgery is the first-line treatment, especially if a person’s quality of life is affected. In cases of tethered cord syndrome, the spinal cord is detached from the spinal canal by a neurosurgeon (brain and spine specialist). This allows the spinal cord to move freely inside the spinal canal which greatly reduces issues caused by tethered cord syndrome. Occasionally, the spinal cord can become re-tethered, requiring further operations. The risk of complications during surgery is low when performed by an experienced neurosurgeon. After surgery, the wound must be closely monitored to prevent infection.

In mild cases, regular outpatient check-ups and monitoring symptoms are preferred over surgery. Monitoring is also important for post-operative patients. Due to the variety of problems these patients can face, it is best to have a team of experts involved in their care.⁴

Importance of multidisciplinary care

The multidisciplinary team is involved throughout the patient journey. As well as the neurosurgeon, paediatricians (doctor specialising in treating children), urologists (doctor who treats problems with the urinary tract), physiotherapists (healthcare professionals treating problems with movement and function), and orthopaedic surgeons (doctor specialising in problems with the bones and joints) may be involved. Even after surgery, patients with OSD require care from the multidisciplinary team for the rest of their lives. The team manages and plans the patient’s care, adapting to their changing needs, especially during the transition from childhood to adulthood. In the case of tethered cord syndrome, there is approximately a 10% chance of the spinal cord becoming ‘re-tethered’ after surgical correction, requiring further surgical intervention. This is more likely in particularly complex situations.⁴

Often, a physiotherapist will work with the patient to resolve any difficulties with movement and pain they may still have after surgery, with the aim of regaining function and minimising symptoms. As well as physical problems, patients with OSD and their families may struggle psychologically. Therefore, the healthcare team should also take into account the concerns and expectations of the whole family so that they can best support the patient.⁴

Quality of Life

An occult spinal abnormality can go unnoticed and cause no symptoms at all. However, if problems do arise as a result of the malformation, surgery can be effective, and early intervention will ensure that the individual can still live an average, healthy life. Sometimes, damage to the nerves is permanent; however, physiotherapy and input from neurologists, nurses, and urologists can ensure effective management of symptoms. Hence, lifelong multidisciplinary care is important.^4,7

Epidemiology

Generally, spinal dysraphism affects around 1 in 1000 babies and is more common in females than in males.^4,8 Closed dysraphism is significantly more common than open dysraphism.⁴ Genes likely play a big part in the development of spinal malformations, but scientists have not yet found an exact cause of OSD. The mother’s health before and during pregnancy also plays an important role; some risk factors include obesity, poor diet, smoking, lack of exercise, and mental stress. Folic acid is thought to prevent the development of spinal dysraphism; therefore, supplementation before and during preganancy is strongly recommended. Certain drugs, such as carbamazepine (medication used to treat epilepsy) and valproic acid (medication used to treat bipolar disorder, epilepsy, and migraines), may increase the risk of spinal dysraphism in the unborn child. Moreover, if a child is born with a spinal dysraphism, the risk of spinal dysraphism increases to 1 in 20 for subsequent pregnancies.^4,8,9

Summary

To conclude, OSD is a hidden form of spinal dysraphism and encompasses a range of spinal malformations. With only a few visible skin signs, if any, the conditioncan go unnoticed until further investigation later in life, when symptoms start to become apparent and affect the individual’s daily life. Symptoms can be related to loss of function, bladder issues, and pain; more serious cases of OSD are associated with tethered cord syndrome. Usually, an ultrasound or an MRI scan is used to take a closer look at the spine, spinal cord, and surrounding tissue. If the spinal cord is damaged, quality of life can be decreased.

However, investigating any symptoms promptly and undergoing surgery is extremely effective as this can reduce or even remove the pain, and recover lost functions caused by the deformity. Sometimes, symptoms and loss of function can persist even after surgery, so a multidisciplinary team including doctors, physiotherapists and nurses is essential to the lifelong care and wellbeing of the patient, as well as their family. With the right support, patients living with symptoms caused by OSD can live a normal, healthy life.