Case Presentation: 40 year old male patient with known history of IVDU and Hepatitis C infection presented with shortness of breath, worsening bilateral weakness in his lower limbs and difficulty walking for two weeks prior to admission.
On initial exam, patient had rhonchi and lower limb weakness (4/5). Labs were within normal limits. Patient had progressive hypoxemia and was intubated, developed opthalmoplegia and worsening lower motor weakness with areflexia involving both the proximal and distal muscle groups. MRI and CT scan showed no intracranial abnormality. LP was done which showed no albuminocytologic dissociation, a complete infectious workup, as well as TSH and vitamin B12 were normal. The spinal fluid was sent for ganglioside antibody panel and the patient was positive for GQ1b antibody, also known as Asialo GM1 antibody. A diagnosis of Miller Fisher syndrome (MFS) was made. His presentation was complicated by aspiration pneumonia that was treated with antibiotics.The patient received IVIG over the course of four days which resolved the ophthalmoplegia and slightly improved the overall weakness. Later the patient also carried the diagnosis of acute motor axonal neuropathy (AMAN) which was made after EMG studies and nerve conduction studies were done. Eventually the patient had a tracheostomy placed and rehabilitation was started, patients weakness in the proximal muscles groups remained profound.
Discussion: Dr. C. Miller Fisher described this variant of GBS in 1956. Patients have ataxia, eye muscle weakness, areflexia but usually no limb weakness which makes this patient’s presentation atypical and rather an overlap between MFS and AMAN would be the more likely diagnosis. MFS as well as AMAN are autoimmune and differ from Gullian Barre syndrome (GBS) in regards to the mechanism of injury.For MFS pathophysiology differs from typical GBS as anti-GQ1b ganglioside antibodies and the membrane attack complexes target the presynaptic motor nerve terminal axon and surrounding Schwann cells. Thus the axon is preferentially injured in MFS in contrast to the segmental myelin loss seen in most forms of GBS, a similar pathophysiology is also seen in AMAN. The diagnosis of MFS in this case was made by detection of anti-GQ1b combined with the presenting symptom even in the absence of albumiocytologic dissociation while diagnosis of AMAN was by the abnormal EMG studies showing motor neuropathy
The recovery in GBS occurs much more rapidly as damage is only to myelin which grows back in a few weeks, however its subtypes the axon has to recover and this, which is possible in the peripheral nervous system, takes extended periods of time and in some cases the axon might not fully recover. The medical therapy is as in GBS mainly plasmapheresis or IVIG as mainstay of treatment.
Conclusions: Recognition of the prescence of GBS subtypes such as MFS and AMAN is important to have an accurate prognosis and an expected recovery time. GQ1B antibody testing can help diagnose MFS in the abscence of albuminocytologic dissociation. Treatment of these subtypes is similar to classical GBS with mainstay of treatment being IVIG and/or plasmaphoresis
Miller Fisher syndrome mean recovery rate is 10.1 weeks