What is Fatty Filum Terminale?
Fatty filum terminale (FFT), also known as lipoma of the filum terminale, is a congenital condition in which there is an abnormal accumulation of fat within the filum terminale - a fibrous, thread-like structure that extends from the conus medullaris (the lower end of the spinal cord) to the coccyx (the triangular bony structure that makes up the final segment of the vertebral column). This condition is often associated with tethered cord syndrome, where the spinal cord is abnormally anchored, restricting its movement, and potentially leading to neurological symptoms. FFT is the most common form of spinal cord tethering.
Causes of Fatty Filum Terminale
Fatty infiltration of the filum terminale is thought to occur as a result of a developmental error in mesodermal cell migration during fetal development. The filum terminale is normally a thin, elastic structure, but in FFT, it contains excessive fat, making it thicker and less flexible. This abnormality can lead to spinal cord tethering, where the spinal cord is abnormally stretched, potentially impairing function.
Symptoms of Fatty Filum Terminale
Mild cases of fatty filum terminale are often asymptomatic. However, severe cases of FFT may present with symptoms such as:
- Lower back pain
- Weakness or numbness in the legs
- Bladder and bowel dysfunction
- Foot deformities (e.g., cavus foot, clubfoot)
- Scoliosis
- Gait abnormalities
Diagnosis of Fatty Filum Terminale
The diagnosis of fatty filum terminale is primarily made through MRI of the lumbosacral spine, which is the gold standard imaging modality. MRI typically reveals a thickened filum terminale (>2 mm) containing fat, confirming the condition. In neonates and infants, spinal ultrasound may be used for early screening before the spine ossifies. Clinically, many cases are asymptomatic and discovered incidentally, but in symptomatic individuals, evaluation focuses on signs of tethered cord syndrome, including low back pain, leg weakness, sensory deficits, bladder or bowel dysfunction, and foot deformities. A detailed neurological examination is crucial to assess any motor, sensory, or reflex abnormalities. In cases of suspected tethered cord, additional imaging or neurophysiological studies may be performed to evaluate spinal cord tension.
Treatment for Fatty Filum Terminale
Treatment for fatty filum terminale depends on whether it is symptomatic or asymptomatic. Asymptomatic cases typically do not require treatment and are managed with regular monitoring through imaging. However, if symptoms of tethered cord syndrome develop, surgical intervention is recommended. The standard procedure is filum terminale sectioning (FTS), a minimally invasive surgery that releases tension on the spinal cord by cutting the thickened filum. This helps prevent neurological deterioration and may improve symptoms such as leg weakness, pain, and bladder dysfunction. Surgery is typically effective in preventing symptom progression and improving quality of life. Postoperative recovery generally includes physical therapy and neurological monitoring to assess symptom improvement and prevent recurrence.
