Neurology of adult alpha - mannosidosis .

The pathogenesis of the cauda equina syndrome of ankylosing spondylitis is unknown. The long duration between the onset of ankylosing spondylitis and neurological symptoms (average 35 years in the Mayo Clinic series') argues against a shared inflammatory cause, as does the relative normality of CSF.' 2 Matthews suggested that arterial pulsations transmitted to the CSF might produce not only the bony erosion and arachnoid diverticula, but also contribute to sacral nerve damage.4 Atrophy of peridural tissues and adherence of dura to adjacent structures, as documented at operation' and pathologically,4 might reduce elasticity and compliance of the caudal sac so impairing its ability to dampen CSF pressure fluctuations. Such excessive pulse pressure in CSF may, over the course of many years, produce the arachnoid diverticula and bony erosions and also have a deleterious effect on nerve roots.' The impression that the cauda equina syndrome more often afflicts those with mild ankylosing spondylitis who remain ambulant may be a reflection of this pathogenetic mechanism. Intrathecal shunting could dampen such pathological pressure oscillations and hence might retard progession of the neuropathy. A review of previous cases of cauda equina syndrome associated with ankylosing spondylitis has indicated that neither steroid treatment nor surgical exploration is of proved utility.2 Moreover, instances of clinical deterioration after surgical intervention on the spine have been documented.' h Neurological improvement after L3-L5 laminectomy and marsupialisation of arachnoid cysts has been reported, but in this single case there was evidence of compression of the nerve roots, a distinctly uncommon finding in the idiopathic cauda equina syndrome of ankylosing spondylitis.7 The use of lumboperitoneal shunting is established for the treatment of idiopathic intracranial hypertension and cranial cerebrospinal fluid fistulae, but previous reports of its use in the cauda equina syndrome of ankylosing spondylitis have not been found. In view of our clinical findings, and the desirability of avoiding radical surgical intervention on the spine in ankylosing spondylitis, we suggest that lumboperitoneal shunting merits consideration in patients with ankylosing spondylitis presenting with an idiopathic cauda equina syndrome. If excessive CSF pressure fluctuations are important in pathogenesis, a case may be made for early surgical intervention by lumboperitoneal shunting in ambulant patients before the development of nerve damage.