Supportive evidence that a significant proportion of patients with CFS may represent a variant of IIH [idiopathic intracranial hypertension]
Based on
CSF pressure readings in CFS patients, in whom headache was a prominent symptom, and their clinical response to CSF drainage, Higgins et al.
[26],
[27],
[28] hypothesized that CFS and IIH may be related. Indeed, their study suggests that if headache is a prominent symptom
in patients diagnosed with CFS, then a substantial proportion of patients with CFS may represent a variant of IIH without
intracranial hypertension or
papilledema, which responds to CSF withdrawal in the same way as IIH patients do. Higgins et al.
[27] measured CSF pressure by
lumbar puncture in 20 patients diagnosed with CFS, in whom headache was a prominent symptom. CSF pressure was found to be>20 cmH2O in five patients, four of whom fulfilled the criteria for IIH. These latter four patients were relabelled as IIH and treated accordingly. Mean CSF pressure was 19 cmH2O, which is towards the high end of normal
[27]. Even more importantly, the authors also found that CSF withdrawal produced a symptomatic improvement in 17 patients (85%), that is in all five patients whose CSF pressures were>20 cmH2O and in 12 patients whose CSF pressures were between 12 and 20 cmH2O
[27]. This improvement usually developed during, or soon after the procedure and lasted from a few minutes to several weeks. It generally took the form of reduced headache, a heightened alertness and a reduced sense of fatigue
[27]. The authors suggested that incomplete forms of IIH, with average CSF pressures much lower than in the syndrome in full, may manifest as CFS
[26],
[27],
[28].
The improvements noted following CSF drainage in these CFS patients at least suggest a neurological basis of some of their symptoms. However, a curious question remains as to why CFS patients with CSF pressures within the normal range should benefit from lowering of the CSF pressure. CSF withdrawal not only lowers CSF pressure, but also promotes the turnover of CSF, and I believe that CSF drainage may favorably affect the fluid dynamics of the glymphatic system, and that this could be an alternative explanation as to why CSF withdrawal may be beneficial in a subgroup of CFS patients
[29]. As discussed below, this latter view
[29] is now supported by very recent observations confirming that a significant proportion of CFS patients represent a variant of IIH
[30] and that IIH may be considered as a manifestation of “glymphedema” of the brain
[31].
