This literature report (initial receipt: 30-Apr-2013) concerns an 85-year-old male patient who had a medical history of congestive heart failure and idiopathic pulmonary fibrosis. He had no history of illicit drug use, excessive alcohol consumption, toxic exposures or family history of neurologic disorders. On an unspecified date, the patient received influenza vaccine (manufacturer and batch number not specified). On an unspecified date, 1 week after vaccination the patient developed tingling in his feet. 1 week later he developed a similar sensation in both hands. He reported difficulty unbuttoning his shirt and unsteadiness when walking. He had no prior similar symptoms, preceding illnesses, or recent changes in his health or medications. On examination, he had no cranial nerve deficits and full strength. He had preserved light touch, temperature, and pinprick sensation, but symmetrically diminished vibration sense and proprioception to the level of both wrists and ankles. Reflexes were absent bilaterally in his upper and lower extremities. On pronator drift testing, his arms drifted upward, and his fingers made small involuntary movements. On finger-nose testing the patient had difficulty reaching and maintaining contact with a target, which worsened with eyes closed. He had no Romberg sign, but had mild gait instability. The patient's gait unsteadiness, upward drift of the arms with pseudoathetosis of the fingers (subtle movements suggestive of a proprioceptive deficit), and worsening of finger-nose testing with eyes closed suggest a sensory ataxia. Sensory ataxia, diminished vibration sense, decreased proprioception, and areflexia localized to the posterior columns, large fibers of peripheral nerves, or intervening dorsal root ganglia or nerve roots; the bilaterality, symmetry, and areflexia made a supratentorial etiology improbable. Before referral to the neurologist, the patient underwent laboratory evaluation for etiologies of peripheral neuropathy, revealing normal vitamin B12, thyroid stimulating hormone, hemoglobin A1C, serum and urine protein electrophoresis, and liver enzymes. Given the rapidly evolving nature of his symptoms and absent reflexes, he was admitted due to concern for possible Guillain-Barre syndrome (GBS). CSF analysis to assess for inflammation or infection revealed normal glucose (60 mg/dL), mildly elevated protein (64.2 mg/dL), and no red or white blood cells. Electromyography (EMG) and nerve conduction studies (NCS) were performed to distinguish between axonal and demyelinating etiologies of presumed polyneuropathy. NCS demonstrated reduced amplitudes of sensory nerve action potentials (SNAPs) in the sural (left 3.3 mV, right 0.60 mV), superficial peroneal (left 3.7 mV, right 3.3 mV), median (left 6.0 mV, right 6.1 mV), and ulnar nerves (left not recordable, right 5.2 mV); slightly reduced amplitudes of combined motor action potentials (CMAPs) of bilateral median (left 4.5 mV, right 2.5 mV), left ulnar (3.4 mV), and bilateral peroneal nerves (left 1.7 mV, right 1.9 mV); and normal nerve conduction velocities (NCV), distal latencies, and F waves. EMG was normal in bilateral tibialis anterior, left first dorsal interosseous, and left extensor digitorum brevis muscles. Due to the lack of weakness and bulbar symptoms and the NCS lacking features of demyelination with preserved F waves, GBS and subtypes of GBS including acute inflammatory demyelinating polyradiculoneuropathies (AIDP) and AIDP variants including Miller Fisher syndrome were ruled out. He underwent extensive but unrevealing evaluation for possible autoimmune, infectious, or paraneoplastic processes (serum antinuclear antibodies, SS-A [Ro], and SS-B [La]; rapid plasma reagin and HIV; anti-Hu, anti-GQ1B, and anti-GM1 autoantibodies; and computed tomography (CT) of the chest, abdomen, and pelvis). Although the etiology of his illness was unclear, intravenous immunoglobulin (IVIg) 0.4 g/kg/day was administered for 5 days. His symptoms remained stable and he was discharged for rehabilitation. He initially noted improvement in his gait and only minimal persistent numbness in his hands and feet. One month later, however, his gait acutely worsened over several days, such that he was too unsteady to walk or stand unassisted. He had a Romberg sign, swayed from side to side when standing, and had a magnetic gait. His sensory, motor, and reflex examinations were otherwise unchanged from his initial examination. The differential diagnosis of the patient's progressive sensory symptoms includes chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and ganglionopathy. Ganglionopathy was diagnosed as it presents with sensory ataxia and deficits in proprioception and vibration sense with reduced SNAPs all seen in the patient. EMG/NCS were repeated and demonstrated relatively unchanged SNAPs and CMAPs compared to his prior NCS. Since worsening axonal neuropathy or ganglionopathy would have been expected to result in further decrement in his SNAPs, his clinical progression in the setting of stable electrodiagnostic studies suggested a more proximal lesion at the level of the nerve roots or posterior columns. In this patient, somatosensory evoked potentials (SSEPs) revealed no reproducible waveforms at any site. Given the presence of SNAPs on routine NCS, the absence of SSEPs suggests block of conduction more proximally (e.g., at the level of proximal nerve roots or posterior columns). Magnetic Resonance Imaging (MRI) of the spine with gadolinium was performed, demonstrating enhancement of numerous lumbosacral nerve roots and dorsal root ganglia with a normal-appearing spinal cord. Nerve biopsy was proposed, but deferred by the patient and his family. This constellation of clinical, electrodiagnostic, and imaging features is suggestive of chronic immune sensory polyradiculopathy (CISP). He was treated with another course of 5 days of IVIg followed by 1 g/kg over 2 days monthly for 4 months and prednisone 60 mg daily. His neurologic status did not improve with therapy, suggesting that he had developed irreversible damage to his proximal nerve segments. He died several months later from complications of his underlying cardiopulmonary disease.