Unraveling the cause of microspurs in spontaneous intracranial hypotension type 1: discogenic origin or calcified Hofmann's ligament?

Objective Spontaneous intracranial hypotension (SIH) with a ventral CSF leak (type 1) is believed to be caused by discogenic microspurs. Recently, this hypothesis was questioned, in which Hofmann's ligament, a fibrous connective tissue between the dura and posterior longitudinal ligament, was claimed to be the cause of a spinal dural tear. The primary objective of this study was to determine whether SIH type 1 lesions arise from a discogenic source or from fibrotic tissue.Methods Patients with ventral CSF leaks treated at the authors' institution, in whom histopathological reports on microspurs were available, were included. All histopathological analyses were repeated and tissues classified into either a fibrotic (Hofmann's ligament) or discogenic group. Correlation analysis of microspur localization in the spine and their origin was conducted. Microspur length and Hounsfield units (HUs) on CT were compared between both groups.Results Twenty-seven patients (19 women, 8 men) with a median age of 57 (IQR 46-64) years were analyzed. Nine microspurs were identified originating from fibrous tissues (Hofmann's ligament) and 13 microspurs were of discogenic origin, while 5 microspurs could not be classified into either group. Nine microspurs were found at the cervicothoracic or thoracolumbar junction, while 18 were located within the midthoracic spine. The location of the microspurs did not correlate with the histopathological origin of the microspur (p = 0.29). The length of a microspur (p = 0.29) as well as its density measured in HUs (p = 0.90) did not show a statistically significant difference between the fibrous and discogenic groups.Conclusions These findings confirm that microspurs in patients with ventral CSF leaks originate from both the intervertebral disc and fibrous epidural ligament, suggestive of Hofmann's ligament.